Component Separations in Polymerization

ABSTRACT

A process for component separation in a polymer production system, comprising separating a polymerization product stream into a gas stream and a polymer stream, wherein the gas stream comprises ethane and unreacted ethylene, distilling the gas stream into a light hydrocarbon stream, wherein the light hydrocarbon stream comprises ethane and unreacted ethylene, contacting the light hydrocarbon stream with an absorption solvent system, wherein at least a portion of the unreacted ethylene from the light hydrocarbon stream is absorbed by the absorption solvent system, and recovering a waste gas stream from the absorption solvent system, wherein the waste gas stream comprises ethane, hydrogen, or combinations thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 15/014,885 filed Feb. 3, 2016, published as U.S.2016/0152745 A1, which is a continuation of and claims priority to U.S.patent application Ser. No. 14/725,991 filed May 29, 2015, now U.S. Pat.No. 9,284,430 B2, which is a continuation of and claims priority to U.S.patent application Ser. No. 13/447,003 filed on Apr. 13, 2012, now U.S.Pat. No. 9,108,147 B2, which is a continuation-in-part of U.S. patentapplication Ser. No. 12/905,966 filed on Oct. 15, 2010, now U.S. Pat.No. 8,410,329 B2, which are hereby incorporated by reference in theirentirety for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

Field of the Invention

This disclosure generally relates to the production of polyethylene.More specifically, this disclosure relates to systems and processes forimproving polyethylene production efficiency by decreasing ethylenelosses.

Background of the Invention

The production of polymers such as polyethylene from light gasesrequires a high purity feedstock of monomers and comonomers. Due to thesmall differences in boiling points between the light gases in such afeedstock, industrial production of a high purity feedstock may requirethe operation of multiple distillation columns, high pressures, andcryogenic temperatures. As such, the energy costs associated withfeedstock purification represent a significant proportion of the totalcost for the production of such polymers. Further, the infrastructurerequired for producing, maintaining, and recycling high purity feedstockis a significant portion of the associated capital cost.

In order to offset some of the costs and maximize production, it can beuseful to reclaim and/or recycle any unreacted feedstock gases,especially the light hydrocarbon reactants, such as ethylene. Gasescomprising unreacted monomers may be separated from the polymer afterthe polymerization reaction. The polymer is processed while theunreacted monomers are recovered from the gases that are reclaimedfollowing the polymerization reaction. To accomplish this, the reclaimedgas streams have conventionally either been routed through apurification process or redirected through other redundant processingsteps. In either case, conventional processes of recovering monomer havenecessitated energetically unfavorable and expensive processes.

Consequently, there is a need for high-efficiency separation of ethylenefrom a recycle stream.

BRIEF SUMMARY

Disclosed herein is a process for component separation in a polymerproduction system, comprising separating a polymerization product streaminto a gas stream and a polymer stream, wherein the gas stream comprisesethane and unreacted ethylene, distilling the gas stream into a lighthydrocarbon stream, wherein the light hydrocarbon stream comprisesethane and unreacted ethylene, contacting the light hydrocarbon streamwith an absorption solvent system, wherein at least a portion of theunreacted ethylene from the light hydrocarbon stream is absorbed by theabsorption solvent system, and recovering a waste gas stream from theabsorption solvent system, wherein the waste gas stream comprisesethane, hydrogen, or combinations thereof.

Also disclosed herein is a process for component separation in a polymerproduction system, comprising separating a polymerization product streaminto a gas stream and a polymer stream, wherein the gas stream comprisesethane and unreacted ethylene, distilling the gas stream into anintermediate hydrocarbon stream and a first bottoms stream, wherein theintermediate hydrocarbon stream comprises ethane, ethylene, andisobutene, distilling the intermediate hydrocarbon stream into a lighthydrocarbon stream and a second bottoms stream, wherein the lighthydrocarbon stream comprises ethane and ethylene, contacting the lighthydrocarbon stream with an absorption solvent system, wherein at least aportion of the unreacted ethylene from the light hydrocarbon stream isabsorbed by the absorption solvent system, and recovering a waste gasstream from the absorption solvent system, wherein the waste gas streamcomprises ethane, hydrogen, or combinations thereof.

Further disclosed herein is a process for component separation in apolymer production system, comprising polymerizing olefin monomers in afirst polymerization reactor to yield a mid-polymerization productstream, separating the mid-polymerization product stream into a mid-gasstream and a mid-polymer stream, wherein the mid-gas stream comprisesethane, unreacted ethylene, and hydrogen, and polymerizing themid-polymer stream in a second polymerization reactor.

Further disclosed herein is a process for component separation in apolymer production system, comprising polymerizing olefin monomers in afirst polymerization reactor, separating a mid-polymerization productstream into a mid-gas stream and a mid-polymer stream, wherein themid-gas stream comprises ethane and unreacted ethylene, polymerizing themid-polymer stream in a second polymerization reactor, and introducing ascavenger prior to the second polymerization reactor.

Further disclosed herein is a process for component separation in apolymer production system, comprising polymerizing olefin monomers in afirst polymerization reactor to yield a mid-polymerization productstream, degassing at least a portion of hydrogen from themid-polymerization product stream to yield a hydrogen-reduced productstream, separating the hydrogen-reduced product stream into a mid-gasstream and a mid-polymer stream, wherein the mid-gas stream comprisesethane and unreacted ethylene, and polymerizing the mid-polymer streamin a second polymerization reactor.

The foregoing has outlined rather broadly the features and technicaladvantages of the disclosed inventive subject matter in order that thefollowing detailed description may be better understood. The variouscharacteristics described above, as well as other features, will bereadily apparent to those skilled in the art upon reading the followingdetailed description of the preferred embodiments, and by referring tothe accompanying drawings.

DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the disclosedprocesses and systems, reference will now be made to the accompanyingdrawings in which:

FIG. 1 illustrates a schematic of a first embodiment of a polyethyleneproduction system;

FIG. 2 illustrates a schematic of a second embodiment of a polyethyleneproduction system;

FIG. 3 illustrates a schematic of a third embodiment of a polyethyleneproduction system;

FIG. 4 illustrates a schematic of a fourth embodiment of a polyethyleneproduction system;

FIG. 5 illustrates a schematic of a fifth embodiment of a polyethyleneproduction system;

FIG. 6 illustrates a flow diagram of a first embodiment of apolyethylene production process;

FIG. 7 illustrates a flow diagram of a second embodiment of apolyethylene production process;

FIG. 8 illustrates a flow diagram of a third embodiment of apolyethylene production process;

FIG. 9 illustrates a flow diagram of a fourth embodiment of apolyethylene production process;

FIG. 10 illustrates a schematic of an embodiment of an absorptionreactor having a pressure swing absorption configuration;

FIG. 11 is a graph illustrating solubility versus temperature forethylene and ethane in an absorption solvent system;

FIG. 12 illustrates a schematic of an embodiment of a simulatedabsorption system; and

FIG. 13 illustrates a schematic of an embodiment of a simulatedabsorption system.

DETAILED DESCRIPTION

Disclosed herein are systems, apparatuses, and processes related to theproduction of polyethylene with improved efficiency. The systems,apparatuses, and processes are generally related to the separation of afirst chemical component or compound from a composition resulting fromthe production of polyethylene and comprising the first chemicalcomponent or compound and one or more other chemical components,compounds, or the like.

Referring to FIG. 1, a first polyethylene production (PEP) system 100 isdisclosed. PEP system 100 generally comprises a purifier 102, reactors104, 106, a separator 108, a processor 110, a distillation column 122,an absorption reactor 116, and a processing device 114. In the PEPembodiments disclosed herein, various system components may be in fluidcommunication via one or more conduits (e.g., pipes, tubing, flow lines,etc.) suitable for the conveyance of a particular stream, for example asshow in detail by the numbered streams in FIGS. 1-5, 10, 12-13.

In the embodiment of FIG. 1, a feed stream 10 may be communicated to thepurifier 102. A purified feed stream 11 may be communicated from thepurifier 102 to one or more of the reactors 104, 106. Where such asystem comprises two or more reactors, a reactor stream 15 may becommunicated from reactor 104 to reactor 106. Hydrogen may be introducedinto reactor 106 in stream 21. A polymerization product stream 12 may becommunicated from one or more of the reactors 104, 106 to the separator108. A polymer stream 14 may be communicated from the separator 108 tothe processor 110. A product stream 16 may be emitted from the processor110. A gas stream 18 may be communicated from the separator 108 to thedistillation column 122. A distillation bottoms stream 23 may be emittedfrom the distillation column 122, and a side stream 27 may be emittedfrom the distillation column 122. A light hydrocarbon stream 25 may beemitted from the distillation column 122 and communicated to theabsorption reactor 116. A waste gas stream 20 may be communicated fromthe absorption reactor 116 to the processing device 114 and a recyclestream 22 may be communicated from the absorption reactor 116 to otherlocations in the system 100, for example, to the purifier 102 via theseparator 108. In the case of recycle to the purifier 102 via theseparator 108, recycle stream 22 may be communicated from the absorptionreactor 116 to the separator 108, and a stream may be communicated fromthe separator 108 to the purifier 102.

Referring to FIG. 2, a second PEP system 200 is disclosed, which has anumber of system components common with PEP 100. In the alternativeembodiment illustrated by FIG. 2, the second PEP system 200 additionallycomprises a deoxygenator 118. Alternatively to the first PEP system 100(as illustrated in FIG. 1), in the embodiment illustrated by FIG. 2, thegas stream 18 may be communicated to the deoxygenator 118. A treated gasstream 26 may be communicated from the deoxygenator 118 to thedistillation column 122. It is contemplated that embodiments of theinventive subject matter may operate with or without the deoxygenator118 as may be suitable for gaseous components in gas stream 18.

In the alternative embodiment illustrated by FIG. 2, the second PEPsystem 200 additionally comprises a distillation column 124. Inembodiments comprising distillation columns 122 and 124, distillationcolumn 122 may be referred to as a first distillation column or a heavydistillation column, and distillation column 124 may be referred to as asecond distillation column or a light distillation column. As shown inFIG. 2, treated gas stream 26 (and optionally, gas stream 18 forembodiments having no deoxygenator 118) may be communicated todistillation column 122. Intermediate hydrocarbon stream 29 may becommunicated from distillation column 122 to distillation column 124.Distillation bottoms stream 23 may be emitted from distillation column122. Distillation bottoms stream 33, and optionally, side stream 31 maybe emitted from distillation column 124. Light hydrocarbon stream 25 maybe emitted from distillation column 124 to the absorption reactor 116.

Referring to FIG. 3, a third. PEP system 300 is disclosed, which has anumber of system components in common with PEP systems 100 and 200.System components downstream of polymerization product stream 12, suchas those shown in FIGS. 1 and 2, are not included in FIG. 3; however, itis contemplated that embodiments such as system 300 may include suchdownstream components in the various embodiments disclosed. In thealternative embodiment illustrated by FIG. 3, the third PEP system 300alternatively comprises a separator 105 between reactor 104 and reactor106. A scavenger may be introduced into system via stream 35. Stream 35may communicate with mid-polymerization product stream 15 to separator105, where the mid-polymerization product stream 15 may be separatedinto mid-gas stream 19 and mid-polymer stream 17. Mid-polymer stream 17may communicate to reactor 106, which emits polymerization productstream 12. Mid-gas stream 19 may be communicated to absorption reactor116, which emits waste stream 20, absorbent stream 30, and recyclestream 22. The waste stream 20 may be communicated from the absorptionreactor 116 to the processing device 114, and the recycle stream 22 maybe communicated from the absorption reactor 116 to other locations inthe system 300, as described for recycle stream 22 in FIG. 1.

Referring to FIG. 4, a fourth PEP system 400 is disclosed, which has anumber of system components common with PEP system 300. Systemcomponents downstream of polymerization product stream 12, such as thoseshown in FIGS. 1 and 2, are not included in FIG. 4; however, it iscontemplated that embodiments such as system 400 may include suchdownstream components in the various embodiments disclosed. In thealternative embodiment illustrated in FIG. 4, the fourth PEP system 400alternatively comprises separator 126. Reactor 104 may emitmid-polymerization product stream 15, which may be communicated toseparator 126. Hydrogen stream 37 may be emitted from separator 126 andhydrogen-reduced product stream 39 may be communicated from separator126 to separator 105.

Referring to FIG. 5, a fifth PEP system 500 is disclosed, which has anumber of system components common with PEP systems 300 and 400. Systemcomponents downstream of polymerization product stream 12, such as thoseshown in FIGS. 1 and 2, are not included in FIG. 5; however, it iscontemplated that embodiments such as system 500 may include suchdownstream components in the various embodiments disclosed. In thealternative embodiment illustrated by FIG. 5, the fifth PEP system 500additionally comprises a regenerator 120 (e.g., a desorption vessel).Alternatively to PEP systems 100, 200, 300, and 400, in the embodimentillustrated in FIG. 5, a complexed stream 28 may be communicated fromthe absorption reactor 116 to the regenerator 120. A recycle stream 22may be communicated to other locations in the system 500, for example,to the purifier 102 via a separator (as discussed in FIG. 1). Aregenerated absorbent stream 30 may be communicated from the regenerator120 to the absorption reactor 116. Although the regenerator 120 is shownin FIG. 5 in conjunction with the absorption reactor 116, it isadditionally contemplated that a regenerator may be used in conjunctionwith any of the absorption reactors 116 of the embodiments of FIGS. 1through 4. Additionally, it is contemplated the absorption reactor 116of FIG. 5 may be configured to operate without regenerator 120.

A temperature of lean solvent may be taken from stream 30 in FIG. 5. Thetemperature of the absorption reactor 116 may depend on a temperature ofgas stream 18, a temperature of lean solvent in stream 30, a heat ofsolution, and a heat of reaction. In the disclosed embodiments, the massflow rate of lean solvent in stream 30 may be 50 to 300 times greaterthan a mass flow rate of the gas stream 18. Therefore; the temperatureof the absorption reactor 116 may highly depend on the temperature oflean solvent in the disclosed embodiments.

Various embodiments of suitable PEP systems having been disclosed,embodiments of a PEP process are now disclosed. One or more of theembodiments of a PEP process may be described with reference to one ormore of PEP system 100, PEP system 200, PEP system 300, PEP system 400,and/or PEP system 500. Although a given PEP process may be describedwith reference to one or more embodiments of a PEP system, such adisclosure should not be construed as so-limiting. Although the varioussteps of the processes disclosed herein may be disclosed or illustratedin a particular order, such should not be construed as limiting theperformance of these processes to any particular order unless otherwiseindicated.

Referring to FIG. 6, a first PEP process 600 is illustrated. PEP process600 generally comprises at block 61 purifying a feed stream, at block 62polymerizing monomers of the purified feed stream to form apolymerization product, at block 63 separating the polymerizationproduct into a polymer stream and a gas stream, at block 64 processingthe polymer stream, at block 65 separating at least one gaseouscomponent from the gas stream to form a recycle stream and a wastestream, and at block 66 combusting the waste stream.

As an example, the first PEP process 600 or a portion thereof may beimplemented via the first PEP system 100 (e.g., as illustrated in FIG.1). Referring to FIGS. 1 and 6, in an embodiment the feed stream 10 maycomprise a gaseous reactant, particularly, ethylene. In an embodiment,purifying the feed stream may yield a purified stream 11 comprisingsubstantially pure monomers (e.g., ethylene monomers), comonomers (e.g.,butene-1 comonomers, or combinations thereof. Polymerizing monomers(optionally, comonomers) of the purified stream 11 may yield thepolymerization product stream 12 generally comprising unreacted monomer(e.g., ethylene), optional unreacted comonomer (e.g., butene-1),by-products (e.g., ethane, which may be by-product ethane formed fromethylene and hydrogen), and a polymerization product (e.g., polymer andoptionally, copolymer). Separating the polymerization product stream 12may yield the polymer stream 14 (e.g., polyethylene polymer, copolymer)and the gas stream 18 generally comprising unreacted monomer (e.g.,ethylene monomer and any optional comonomer such as butene-1) andvarious gases (e.g., ethane, hydrogen). Processing the polymer stream 14may yield the product stream 16. Separating at least one gaseouscomponent from the gas stream 18 may yield a recycle stream 22,generally comprising unreacted ethylene monomer (optionally, unreactedcomonomer), and a waste gas stream 20. In an embodiment, separating atleast one gaseous component from the gas stream 18 may comprisedistilling ethylene from the gas stream 18 to yield a light hydrocarbonstream 25. In an embodiment, separating the gas stream 18 mayalternatively or additionally comprise absorbing ethylene from the gasstream 18 to yield the waste gas stream 20 and then liberating theabsorbed ethylene to form the recycle stream 22. The recycle stream 22,comprising ethylene, may be pressurized (e.g., returned to the purifier102 via the separator 108 for pressurization) and re-introduced into aPEP process (e.g., PEP process 600). Combusting the waste gas stream 20may be carried out with a flare as the processing device 114.

Referring to FIG. 7, a second PEP process 700 is illustrated, which hasa number of process steps common with PEP process 600. PEP process 700generally comprises at block 71 purifying a feed stream, at block 72polymerizing monomers of the purified feed stream to form amid-polymerization product, at block 73 separating the polymerizationproduct into a mid-polymer stream and a mid-gas stream, at block 74polymerizing monomers (optionally, comonomers) of the mid-polymerstream, at block 75 separating at least one gaseous component from themid-gas stream to form a recycle stream and a waste stream, and at block76 combusting the waste stream. In the alternative embodimentillustrated by FIG. 7, blocks 63-64 of FIG. 6 are replaced by blocks73-75. Generally, the process 700 of FIG. 7 takes place between reactors104 and 106, whereas the process 600 of FIG. 6 takes place downstream ofreactors 104 and 106.

As an example, the second PEP process 700 or a portion thereof may beimplemented via the third PEP system 300 (e.g., as illustrated in FIG.3). Referring to FIGS. 3 and 7, in an embodiment the feed stream 10 maycomprise a gaseous reactant, particularly, ethylene. In an embodiment,purifying the feed stream may yield a purified stream 11 comprisingsubstantially pure monomers (e.g., ethylene monomers) and optionally,comonomers (e.g., butene-1). Polymerizing monomers of the purifiedstream 11 may yield the mid-polymerization product stream 15 generallycomprising unreacted monomer (e.g., ethylene), optional unreactedcomonomer (e.g., butene-1), by-products (e.g., ethane, which may beby-product ethane formed from ethylene and hydrogen), and apolymerization product (e.g., polymer and optionally, copolymer). Inalternative to the polymerization product stream 12 of FIG. 1, which isdownstream of polymerization reactors 104 and 106, mid-polymerizationproduct stream 15 of the embodiment in FIG. 3 may be betweenpolymerization reactor(s) 104 and polymerization reactor(s) 106.Separating the mid-polymerization product stream 15 may yield themid-polymer stream 17 generally comprising unreacted ethylene, ethane(which may be by-product ethane formed from ethylene and hydrogen) and apolymer (e.g., polyethylene), and the mid-gas stream 19 generallycomprising unreacted monomer (e.g., ethylene monomer), optionally,unreated comonomer (e.g., butene-1 monomer), and various gases (e.g.,ethane, hydrogen). Polymerizing monomers (optionally, comonomers) of themid-polymer stream 17 may yield polymerization product stream 12.Components of polymerization product stream 12 may be processedaccording to embodiments of systems 100 and 200 in FIGS. 1 and 2.Separating at least one gaseous component from the mid-gas stream 19 mayyield a recycle stream 22, generally comprising unreacted ethylenemonomer (optionally, comonomer), and a waste gas stream 20. In anembodiment, separating the at least one gaseous component from mid-gasstream 19 may comprise absorbing ethylene from the mid-gas stream 19 toyield the waste gas stream 20 and then liberating the absorbed ethyleneto form the recycle stream 22. The recycle stream 22, comprisingethylene, may be pressurized and re-introduced (e.g., as described inFIG. 1) into a PEP process (e.g., PEP process 700). Combusting the wastegas stream 20 may be carried out with a flare as the processing device114.

Referring to FIG. 8, a third PEP process 800 is illustrated, which has anumber of process steps common with PEP process 600 (i.e., blocks 61,62, 63, 64, 65, and 66). In the alternative embodiment illustrated byFIG. 8, the PEP process 800 includes block 81 treating a gas stream toform a treated gas stream and at block 65′ separating at least onegaseous component from the treated gas stream to form a recycle streamand a waste stream.

In an embodiment, third PEP process 800 or a portion thereof may beimplemented via the second. PEP system 200 (e.g. as illustrated in FIG.2). Alternatively to the embodiments of FIGS. 1 and 6, in the embodimentof FIGS. 2 and 8, treating the gas stream 18 may yield the treated gasstream 26. In an embodiment, treating the gas stream 18 comprisesdeoxygenating the gas stream 18. Separating at least one gaseouscomponent from the treated gas stream 26 may yield a recycle stream 22,generally comprising unreacted ethylene monomer (optionally, comonomer),a waste gas stream 20, a distillation bottoms stream 23, a distillationbottoms stream 33, and a side stream 31.

Referring to FIG. 9, a fourth PEP process 900 is illustrated, which hasa number of process steps common with PEP process 700. In thealternative embodiment illustrated by FIG. 9, the PEP process 900includes block 91 treating a gas stream (e.g., the mid-gas stream 19) toform a treated gas stream. Block 75 of FIG. 7 is altered at block 75′for separating at least one gaseous component from the treated gasstream to form a complexed stream and a waste gas stream. At block 92,PEP process 900 includes separating the complexed stream into anabsorbent stream and a recycle stream.

In an embodiment, fourth PEP process 900 or a portion thereof may beimplemented via the fifth PEP system 500 (e.g. as illustrated in FIG.5). Alternatively to the embodiments of FIGS. 3 & 7, in the embodimentsof FIGS. 5 and 9, separating at least one gaseous component from thetreated gas stream 41 may yield an unreacted monomer-absorbent (e.g., anethylene-absorbent) in complexed stream 28. In an embodiment, separatingthe unreacted monomer-absorbent complexed stream 28 comprises liberatingthe absorbed ethylene to form a recycle stream 22 and an absorbentstream 30. In the embodiment of FIGS. 5 and 9, separating at least onegaseous component from the treated gas stream 26 may yield an unreactedcomonomer-absorbent (e.g., a butene-1-absorbent) in complexed stream 28.In an embodiment, separating the unreacted comonomer-absorbent incomplexed stream 28 comprises releasing the absorbed comonomer to form arecycle stream 22 and a regenerated absorbent stream 30.

In one or more of the embodiments disclosed herein, purifying a feedstream (e.g., at block 61 or 71) may comprise separating unwantedcompounds and elements from a feed stream comprising ethylene to form apurified feed stream. In an embodiment, the feed stream may compriseethylene and various other gases, such as but not limited to methane,ethane, acetylene, propylene, various other hydrocarbons having three ormore carbon atoms, or combinations thereof. In an embodiment, purifyinga feed stream may comprise any suitable method or process, including thenon-limiting examples filtering, membrane screening, reacting withvarious chemicals, absorbing, adsorbing, distillation(s), orcombinations thereof.

In embodiments as illustrated by FIGS. 1-5, purifying a feed stream maycomprise routing the feed stream 10 to the purifier 102. In one or moreof the embodiments disclosed herein, the purifier 102 may comprise adevice or apparatus suitable for the purification of one or morereactant gases in a feed stream comprising a plurality of potentiallyunwanted gaseous compounds, elements, contaminants, or the like.Non-limiting examples of a suitable purifier 102 may comprise a filter,a membrane, a reactor, an absorbent, a molecular sieve, one or moredistillation columns, or combinations thereof. The purifier 102 may beconfigured to separate ethylene from a stream comprising methane,ethane, acetylene, propane, propylene, water, oxygen various othergaseous hydrocarbons, various contaminants, and/or combinations thereof.

In an embodiment, purifying a feed stream may yield a purified feed 11comprising substantially pure ethylene. In an embodiment, the purifiedfeed stream may comprise less than 25% by total weight of the stream,alternatively, less than about 10%, alternatively, less than about 1.0%of any one or more of nitrogen, oxygen, methane, ethane, propane, orcombinations thereof. As used herein “substantially pure ethylene”refers to a fluid stream comprising at least about 60% ethylene,alternatively, at least about 70% ethylene, alternatively, at leastabout 80% ethylene, alternatively, at least about 90% ethylene,alternatively, at least about 95% ethylene, alternatively, at leastabout 99% ethylene by total weight of the stream, alternatively, atleast about 99.5% ethylene by total weight of the stream. In anembodiment, the feed stream 11 may further comprise trace amounts ofethane, for example, as from a recycle stream as will be discussed.

In one or more of the embodiments disclosed herein, monomers in feedstream 11, mid-polymerization product stream 15, and mid-polymer stream17 may be polymerized. In one or more embodiments, polymerizing monomersof the purified feed (e.g., at blocks 62 and 72) may comprise allowing apolymerization reaction between a plurality of monomers by contacting amonomer or monomers with a catalyst system under conditions suitable forthe formation of a polymer. In one or more of the embodiments disclosedherein, polymerizing comonomers (e.g., at blocks 62 and 72) of thepurified feed may comprise allowing a polymerization reaction between aplurality of comonomers by contacting a comonomer or comonomers with acatalyst system under conditions suitable for the formation of acopolymer. Likewise, in one or more of the embodiments disclosed herein,polymerizing monomers of the mid-polymer stream (e.g., at block 74) maycomprise allowing a polymerization reaction between a plurality ofmonomers by contacting a monomer or monomers with a catalyst systemunder conditions suitable for the formation of a polymer. In one or moreof the embodiments disclosed herein, polymerizing comonomers (e.g., atblock 74) of the mid-polymer stream may comprise allowing apolymerization reaction between a plurality of comonomers by contactinga comonomer or comonomers with a catalyst system under conditionssuitable for the formation of a copolymer. Likewise still, in one ormore of the embodiments disclosed herein, polymerizing monomers of themid-polymerization product may comprise allowing a polymerizationreaction between a plurality of monomers by contacting a monomer ormonomers with a catalyst system under conditions suitable for theformation of a polymer. In one or more of the embodiments disclosedherein, polymerizing comonomers of the mid-polymerization product maycomprise allowing a polymerization reaction between a plurality ofcomonomers by contacting a comonomer or comonomers with a catalystsystem under conditions suitable for the formation of a copolymer.

In embodiments as illustrated by FIGS. 1-5, polymerizing monomers of thepurified teed may comprise routing the feed stream 11 to the one or moreof the polymerization reactors or “reactors” 104, 106. In embodiments asillustrated by FIGS. 1-2, polymerizing monomers of themid-polymerization product may comprise routing the mid-polymerizationproduct stream 15 to polymerization reactor(s) 106. In embodiments asillustrated by FIGS. 1-2, polymerizing monomers of themid-polymerization product may comprise routing the mid-polymerizationproduct stream 15 from polymerization reactor(s) 104 to polymerizationreactor(s) 106. In embodiments as illustrated by FIGS. 3-5, polymerizingmonomers of the mid-polymer stream 17 may comprise routing themid-polymer stream 17 to polymerization reactor(s) 106. In embodimentsas illustrated by FIGS. 3-5, polymerizing monomers of the mid-polymerstream 17 may comprise routing the mid-polymer stream 17 from aseparator 105 to polymerization reactor(s) 106.

In an embodiment, any suitable catalyst system may be employed. Asuitable catalyst system may comprise a catalyst and, optionally, aco-catalyst and/or promoter. Non-limiting examples of suitable catalystsystems include Ziegler Natta catalysts, Ziegler catalysts, chromiumcatalysts, chromium oxide catalysts, chromocene catalysts, metallocenecatalysts, nickel catalysts, or combinations thereof. Catalyst systemssuitable for use in this disclosure have been described, for example, inU.S. Pat. No. 7,619,047 and U.S. Patent Application Publication Nos.2007/0197374, 2009/0004417, 2010/0029872, 2006/0094590, and2010/0041842, each of which is incorporated by reference herein in itsentirety.

In one or more of the embodiments disclosed herein, the reactors 104,106 may comprise any vessel or combination of vessels suitablyconfigured to provide an environment for a chemical reaction (e.g., acontact zone) between monomers (e.g., ethylene) and/or polymers (e.g.,an “active” or growing polymer chain), and optionally comonomers (e.g.,butene-1) and/or copolymers, in the presence of a catalyst to yield apolymer (e.g., a polyethylene polymer) and/or copolymer. Although theembodiments illustrated in FIGS. 1, 2, and 3, illustrate various PEPsystems having two reactors in series, one of skill in the art viewingthis disclosure will recognize that one reactor, alternatively, anysuitable number and/or configuration of reactors, may be employed.

As used herein, the terms “polymerization reactor” or “reactor” includeany polymerization reactor capable of polymerizing olefin monomers orcomonomers to produce homopolymers or copolymers. Such homopolymers andcopolymers are referred to as resins or polymers. The various types ofreactors include those that may be referred to as batch, slurry,gas-phase, solution, high pressure, tubular or autoclave reactors. Gasphase reactors may comprise fluidized bed reactors or staged horizontalreactors. Slurry reactors may comprise vertical or horizontal loops.High pressure reactors may comprise autoclave or tubular reactors.Reactor types can include batch or continuous processes. Continuousprocesses could use intermittent or continuous product discharge.Processes may also include partial or full direct recycle of un-reactedmonomer, unreacted comonomer, and/or diluent.

Polymerization reactor systems of the present disclosure may compriseone type of reactor in a system or multiple reactors of the same ordifferent type. Production of polymers in multiple reactors may includeseveral stages in at least two separate polymerization reactorsinterconnected by transfer stream(s), line(s), apparatus(es) (forexample, a separation vessel(s)) and/or device(s) (for example, a valveor other mechanism) making it possible to transfer the polymersresulting from the first polymerization reactor (e.g., reactor 104) intothe second reactor (e.g., reactor 106). The desired polymerizationconditions in one of the reactors may be different from the operatingconditions of the other reactors. Alternatively, polymerization inmultiple reactors may include the manual transfer of polymer from onereactor to subsequent reactors for continued polymerization. Multiplereactor systems may include any combination including, but not limitedto, multiple loop reactors, multiple gas reactors, a combination of loopand gas reactors, multiple high pressure reactors or a combination ofhigh pressure with loop and/or gas reactors. The multiple reactors maybe operated in series or in parallel.

In embodiments as illustrated in FIGS. 1-5, production of polymers inmultiple reactors may include at least two polymerization reactors 104,106 interconnected by one or more devices or apparatus (e.g., valve,continuous take-off valve, and/or continuous take-off mechanism). Inembodiments as illustrated in FIGS. 1-2, production of polymers inmultiple reactors may include at least two polymerization reactors 104,106 interconnected by one or more streams or lines (e.g.,mid-polymerization product stream 15). In embodiments as illustrated inFIGS. 3-5, production of polymers in multiple reactors may include atleast two polymerization reactors 104, 106 interconnected by one or moreseparator (e.g., separator 105 and/or separator 126) via two or morestreams (e.g., mid-polymerization product stream 15 and mid-polymerstream 17).

According to one aspect, the polymerization reactor system may compriseat least one loop slurry reactor comprising vertical or horizontalloops. Monomer, diluent, catalyst, and optionally any comonomer may becontinuously fed to a loop reactor where polymerization occurs.Generally, continuous processes may comprise the continuous introductionof a monomer, an optional comonomer, a catalyst, and a diluent into apolymerization reactor and the continuous removal from this reactor of asuspension comprising polymer particles and the diluent. Reactoreffluent may be flashed to remove the solid polymer from the liquidsthat comprise the diluent, monomer and/or comonomer. Varioustechnologies may be used for this separation step including but notlimited to, flashing that may include any combination of heat additionand pressure reduction; separation by cyclonic action in either acyclone or hydrocyclone; or separation by centrifugation.

In one or more embodiments, a comonomer may comprise unsaturatedhydrocarbons having 3 to 12 carbon atoms. For example, a comonomer maycomprise propene, butene-1, hexene-1, octenes, or combinations thereof.

A typical slurry polymerization process (also known as the particle formprocess), is disclosed, for example, in U.S. Pat. Nos. 3,248,179,4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415,each of which is incorporated by reference in its entirety herein.

In one or more embodiments, suitable diluents used in slurrypolymerization include, but are not limited to, the monomer, andoptionally, the comonomer, being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable monomer diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. In embodiments, comonomer diluents may comprise unsaturatedhydrocarbons having 3 to 12 carbon atoms. Examples of suitable comonomerdiluents include, but are not limited to propene, butene-1, hexene-1,octenes, or combinations thereof. Some loop polymerization reactions canoccur under bulk conditions where no diluent is used. An example ispolymerization of propylene monomer as disclosed in U.S. Pat. No.5,455,314, which is incorporated by reference herein in its entirety.

According to yet another aspect, the polymerization reactor may compriseat least one gas phase reactor. Such systems may employ a continuousrecycle stream containing one or more monomers continuously cycledthrough a fluidized bed in the presence of the catalyst underpolymerization conditions. A recycle stream may be withdrawn from thefluidized bed and recycled back into the reactor. Simultaneously,polymer product may be withdrawn from the reactor and new or freshmonomer may be added to replace the polymerized monomer. Likewise,copolymer product may optionally be withdrawn from the reactor and newor fresh comonomer may be added to replace polymerized comonomer,polymerized monomer, or combinations thereof. Such gas phase reactorsmay comprise a process for multi-step gas-phase polymerization ofolefins, in which olefins are polymerized in the gaseous phase in atleast two independent gas-phase polymerization zones while feeding acatalyst-containing polymer formed in a first polymerization zone to asecond polymerization zone. One type of gas phase reactor is disclosedin U.S. Pat. Nos. 5,352,749, 4,588,790 and 5,436,304, each of which isincorporated by reference in its entirety herein.

According to still another aspect, a high pressure polymerizationreactor may comprise a tubular reactor or an autoclave reactor. Tubularreactors may have several zones where fresh monomer (optionally,comonomer), initiators, or catalysts may be added. Monomer (optionally,comonomer) may be entrained in an inert gaseous stream and introduced atone zone of the reactor. Initiators, catalysts, and/or catalystcomponents may be entrained in a gaseous stream and introduced atanother zone of the reactor. The gas streams may be intermixed forpolymerization. Heat and pressure may be employed appropriately toobtain optimal polymerization reaction conditions.

According to yet another aspect, the polymerization reactor may comprisea solution polymerization reactor wherein the monomer (optionally,comonomer) may be contacted with the catalyst composition by suitablestirring or other means. A carrier comprising an inert organic diluentor excess monomer (optionally, comonomer) may be employed. If desired,the monomer and/or optional comonomer may be brought in the vapor phaseinto contact with the catalytic reaction product, in the presence orabsence of liquid material. The polymerization zone is maintained attemperatures and pressures that will result in the formation of asolution of the polymer in a reaction medium. Agitation may be employedto obtain better temperature control and to maintain uniformpolymerization mixtures throughout the polymerization zone. Adequatemeans are utilized for dissipating the exothermic heat ofpolymerization.

Polymerization reactors suitable for the disclosed systems and processesmay further comprise any combination of at least one raw material feedsystem, at least one feed system for catalyst or catalyst components,and/or at least one polymer recovery system. Suitable reactor systemsmay further comprise systems for feedstock purification, catalyststorage and preparation, extrusion, reactor cooling, polymer recovery,fractionation, recycle, storage, loadout, laboratory analysis, andprocess control.

Conditions that are controlled for polymerization efficiency and toprovide resin properties include temperature, pressure and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperature may be anytemperature below the de-polymerization temperature according to theGibbs Free energy equation. Typically this includes from about 60° C. toabout 280° C., for example, and from about 70° C. to about 110° C.,depending upon the type of polymerization reactor.

Suitable pressures will also vary according to the reactor andpolymerization type. The pressure for liquid phase polymerizations in aloop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200-500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to 75,000 psig. Polymerization reactors can also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.In an embodiment, polymerization may occur in an environment having asuitable combination of temperature and pressure. For example,polymerization may occur at a pressure in a range from about 550 psi toabout 650 psi, alternatively, about 600 psi to about 625 psi and atemperature in a range from about 170° F. to about 230° F.,alternatively, from about 195° F. to about 220° F.

The concentration of various reactants can be controlled to produceresins with certain physical and mechanical properties. The proposedend-use product that will be formed by the resin and the method offorming that product determines the desired resin properties. Mechanicalproperties include tensile, flexural, impact, creep, stress relaxationand hardness tests. Physical properties include density, molecularweight, molecular weight distribution, melting temperature, glasstransition temperature, temperature melt of crystallization, density,stereoregularity, crack growth, long chain branching and rheologicalmeasurements.

The concentrations and/or partial pressures of monomer, comonomer,hydrogen, co-catalyst, modifiers, and electron donors are important inproducing these resin properties. Comonomer may be used to controlproduct density. Hydrogen may be used to control product molecularweight. Cocatalysts can be used to alkylate, scavenge poisons andcontrol molecular weight. Modifiers can be used to control productproperties and electron donors affect stereoregularity, the molecularweight distribution, or molecular weight. In addition, the concentrationof poisons is minimized because poisons impact the reactions and productproperties.

In an embodiment, polymerizing monomers may comprise introducing asuitable catalyst system into the first and/or second reactor 104, 106,respectively, so as to form a slurry. Alternatively, a suitable catalystsystem may reside in the first and/or second reactor 104, 106,respectively.

As explained above, polymerizing monomers may comprise selectivelymanipulating one or more polymerization reaction conditions to yield agiven polymer product, to yield a polymer product having one or moredesirable properties, to achieve a desired efficiency, to achieve adesired yield, the like, or combinations thereof. Non-limiting examplesof such parameters include temperature, pressure, type and/or quantityof catalyst or cocatalyst, and the concentrations and/or partialpressures of various reactants. In an embodiment, polymerizing monomersof the purified feed 52 may comprise adjusting one or morepolymerization reaction conditions. In an embodiment, polymerizingmonomers may comprise adding ethylene monomer and/or a comonomer such asbutene to the polymerization reactor 106.

In an embodiment, polymerizing monomers may comprise maintaining asuitable temperature, pressure, and/or partial pressure(s) during thepolymerization reaction, alternatively, cycling between a series ofsuitable temperatures, pressures, and/or partials pressure(s) during thepolymerization reaction.

In an embodiment, polymerizing monomers may include introducing hydrogeninto one or more of reactors 104 and 106. For example, FIGS. 1 and 2illustrate hydrogen may be introduced into reactor 106 through stream21. The amount of hydrogen introduced into the reactor 106 may beadjusted so as to obtain, in the diluent, a molar ratio of hydrogen toethylene of 0.001 to 0.1. This molar ratio may be at least 0.004 inreactor 106. In embodiments, this molar ratio may not exceed 0.05. Theratio of the concentration of hydrogen in the diluent in reactor 104 tothe concentration of hydrogen polymerization reactor 106 may be at least20, alternatively, at least 30, alternatively, at least 40,alternatively, not greater than 300, alternatively, not greater than200. Suitable hydrogen concentration control methods and systems aredisclosed in U.S. Pat. No. 6,225,421, which is incorporated herein byreference.

In an embodiment, polymerizing monomers may comprise circulating,flowing, cycling, mixing, agitating, or combinations thereof, themonomers (optionally, comonomers), catalyst system, and/or the slurrywithin and/or between the reactors 104, 106. In an embodiment where themonomers (optionally, comonomers), catalyst system, and/or slurry arecirculated, circulation may be at a velocity (e.g., slurry velocity) offrom about 1 m/s to about 30 m/s, alternatively, from about 2 m/s toabout 17 m/s, alternatively, from about 3 m/s to about 15 m/s.

In an embodiment, polymerizing monomers may comprise configuringreactors 104, 106 to yield a multimodal (e.g., a bimodal) polymer (e.g.,polyethylene). For example, the resultant polymer may comprise both arelatively high molecular weight, low density (HMWLD) polyethylenepolymer and a relatively low molecular weight, high density (LMWHD)polyethylene polymer. For example, various types of suitable polymersmay be characterized as having a various densities. For example, a TypeI may be characterized as having a density in a range of from about0.910 g/cm³ to about 0.925 g/cm³, alternatively, a Type II may becharacterized as having a density from about 0.926 g/cm³ to about 0.940g/cm³, alternatively, a Type III may be characterized as having adensity from about 0.941 g/cm³ to about 0.959 g/cm³, alternatively, aType IV may be characterized as having a density of greater than about0.960 g/cm³.

In an embodiment, polymerizing monomers may comprise polymerizingcomonomers in one or more of polymerization reactors 104, 106.

In embodiments illustrated in FIGS. 1-5, polymerizing monomers of thepurified feed may yield mid-polymerization product stream 15 and/orpolymerization product stream 12. Such a mid-polymerization productstream 15 and/or a polymerization product stream 12 may generallycomprise various solids, semi-solids, volatile and nonvolatile liquids,gases and combinations thereof. In an embodiment, the mid-polymerizationproduct stream 15 and/or the polymerization product stream 12 maycomprise hydrogen, nitrogen, methane, ethylene, ethane, propylene,propane, butane, isobutane, pentane, hexane, hexene-1 and heavierhydrocarbons. In an embodiment, ethylene may be present in a range offrom about 0.1% to about 15%, alternatively, from about 1.5% to about5%, alternatively, about 2% to about 4% by total weight of the stream.Ethane may be present in a range of from about 0.001% to about 4%,alternatively, from about 0.2% to about 0.5% by total weight of thestream. Isobutane may be present in a range from about 80% to about 98%,alternatively, from about 92% to about 96%, alternatively, about 95% bytotal weight of the stream.

The solids and/or liquids may comprise a polymer product (e.g., apolyethylene polymer), often referred to at this stage of the PEPprocess as “polymer fluff.” The gases may comprise unreacted, gaseousreactant monomers or optional comonomers (e.g., unreacted ethylenemonomers, unreacted butene-1 monomers), gaseous waste products, gaseouscontaminants, or combinations thereof.

In one or more of the embodiments disclosed herein, separating thepolymerization product into a polymer stream and a gas stream (e.g., atblock 63) may generally comprise removing any gases from liquids and/orsolids (e.g., the polymer fluff) by any suitable process.

In embodiments as illustrated by FIGS. 1-2, separating thepolymerization product into a polymer stream and a gas stream maycomprise routing the polymerization product steam 12 to the separator108.

In an embodiment, the gas stream 18 may comprise hydrogen, nitrogen,methane, ethylene, ethane, propylene, propane, butane, isobutane,pentane, hexane, hexene-1 and heavier hydrocarbons. In an embodiment,ethylene may be present in a range of from about 0.1% to about 15%,alternatively, from about 1.5% to about 5%, alternatively, about 2% toabout 4% by total weight of the stream. Ethane may be present in a rangeof from about 0.001% to about 4%, alternatively, from about 0.2% toabout 0.5% by total weight of the stream. Isobutane may be present in arange from about 80% to about 98%, alternatively, from about 92% toabout 96%, alternatively, about 95% by total weight of the stream.

In one or more embodiments, separating the mid-polymerization productinto a mid-polymer and a mid-gas stream (e.g., at block 73) maygenerally comprise removing any gases from liquids and/or solids (e.g.,the polymer fluff) by any suitable process.

In embodiments as illustrated in FIGS. 3 and 5, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may be accomplished in a single-step separation comprisingrouting the mid-polymerization product steam 15 to a separator 105.

In embodiments as illustrated in FIG. 3, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may comprise separating at least one gaseous component from themid-polymerization product stream 15. Separating at least one gaseouscomponent from the mid-polymerization product stream 15 may yieldmid-gas stream 19 and mid-polymer stream 17. Mid-polymerization productstream 15 may comprise hydrogen, ethylene, ethane, polymer, isobutane,or combinations thereof. Mid-gas stream 19 may comprise hydrogen,ethylene, ethane or combinations thereof. Mid-polymer stream 17 maycomprise polymer, isobutane, or combinations thereof.

In embodiments as illustrated in FIG. 3, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may comprise reducing a pressure of the mid-polymerizationproduct so as to flash ethylene, hydrogen, ethane, or combinationsthereof. Mid-polymerization product stream 15 may comprise hydrogen,ethylene, ethane, polymer, isobutane, or combinations thereof. Separator105 may create a reduction in pressure so that ethylene, hydrogen, andethane separate, or flash, from the mid-polymerization product so as toyield mid-gas stream 19 comprising hydrogen, ethylene, and ethane.

In embodiments as illustrated in FIG. 5, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may comprise introducing a scavenger prior to reactor 106. Inembodiments, the scavenger may reduce a concentration of a component,for example, hydrogen. Embodiments illustrated by FIGS. 3 and 5 showstream 35 may be introduced prior to the reactor 106 via, for example,mid-polymerization product stream 15. Alternatively, stream 35 may beintroduced in separator 105 or mid-polymer stream 17. Stream 35 maycomprise a scavenger. In embodiments, the scavenger may comprise acatalyst. In embodiments, the catalyst may comprise a hydrogenationcatalyst. Without intending to be bound by theory, a scavenger may actto consume hydrogen to form ethane which may reduce the hydrogenconcentration, even to zero concentration. In embodiments, thehydrogenation catalyst may have a low activity with respect to thepolymerization of polyethylene. The hydrogenation catalyst may comprisea metallocene catalyst of the general formula:

Cp₂MX_(n)

where Cp is a substituted cyclopentadienyl group; M is a transitionmetal from Group IVB of the Periodic Table of vanadium; X is a halogenor a hydrocarbyl group having from 1 to 10 carbon atoms; and n is thevalency of the metal M minus 2. In embodiments, the metallocene catalystmay comprise Cp₂TiCl₂, also known as titanocene dichloride. Themetallocene catalyst may be introduced in an amount of from 2 to 50 ppmby weight of inert diluent in the mid-polymerization product stream 15,alternatively, from 2 to 20 ppm.

In embodiments as illustrated in FIG. 5, reducing a concentration ofhydrogen in a stream prior to the second polymerization reactor 106 witha scavenger may improve polymer production capability, for example, mayproduce a relatively higher molecular weight polymer in polymerizationreactor 106 than in polymerization reactor 104. For example, inembodiments where a relatively higher molecular weight polymer inreactor 106 is desired, typically no additional hydrogen is added to thereactor 106 because increased hydrogen concentration in reactor 106 isgenerally detrimental to producing higher molecular weight polymer.Instead of introducing hydrogen in such embodiments, a hydrogenationcatalyst may be introduced in, or prior to, the reactor 106. Embodimentsillustrated by FIGS. 3 and 5 show the hydrogenation catalyst may beintroduced in stream 35 prior to reactor 106. In one or moreembodiments, the polymer produced may comprise polyethylene. In suchembodiments, a Zeigler-Natty catalyst may be used as the polymerizationcatalyst, and the hydrogenation catalyst introduced through stream 35may comprise a metallocene catalyst. The amount of metallocene catalystused may be such that the mass ratio of metallocene catalyst toZeigler-Natty catalyst (i.e., g metallocene/g Zeigler-Natta) may have arange of from about 0.1 to about 2.0, preferably from about 0.25 toabout 1.5, more preferably about 0.5-1.0. In an embodiment, themetallocene catalyst may comprise an unbridged metallocene. In anembodiment, an unbridged metallocene may comprise bis (cyclopentadienyl)titanium dichloride, also referred to as titanocene dichloride. Suitablehydrogenation catalysts are disclosed in U.S. Pat. Nos. 6,730,751,6,221,982, and 6,291,601, which are incorporated herein by reference.

In embodiments as illustrated in FIG. 5, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may further comprise separating at least one gaseous componentfrom the mid-polymerization product stream. In such embodiments,mid-polymerization product stream 15 entering the separator 105 maycomprise unreacted hydrogen, unconverted ethylene, ethane, polymer,isobutane, or combinations thereof. Mid-gas stream 19 may comprisehydrogen, ethylene, ethane, or combinations thereof, and mid-polymerstream 17 may comprise polymer, isobutane, or combinations thereof. Theamount of ethane in mid-gas stream 19 may be greater than the amount ofunreacted hydrogen and/or unconverted ethylene.

In embodiments as illustrated in FIG. 4, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream (e.g., at block 73) may be accomplished in a two-step separationcomprising routing the mid-polymerization product stream 15 to separator126 and routing a hydrogen-reduced product stream 39 from separator 126to separator 105.

In embodiments as illustrated in FIG. 4, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may comprise degassing at least a portion of hydrogen from themid-polymerization product. Embodiments as illustrated by FIG. 4 show aseparator 126 may yield streams 37 and 39. Stream 37 may compriseremoved hydrogen, and stream 39 may comprise hydrogen-reduced product.Separator 126 may degas at least a portion of hydrogen frommid-polymerization product stream 15 via a pressure reduction. Thereduction in pressure may occur at temperature of less than or equal tothe polymerization temperature in the reactor 104, alternatively;greater than 20° C., alternatively, at least 40° C. The reduction inpressure may occur at a pressure less than the pressure in reactor 104.The reduction in pressure may be less than 1.5 MPa. The reduction inpressure may be at least 0.1 MPa. The amount of hydrogen remaining inhydrogen-reduced stream 39 of FIG. 4 may be less than 1% by weight ofthe amount of hydrogen initially present in the mixture withdrawn fromthe reactor 104, alternatively, less than 0.5% by weight, alternatively,0 wt % by weight. Suitable degassing conditions and equipment aredisclosed in U.S. Pat. No. 6,225,412; which is incorporated herein byreference.

In embodiments as illustrated in FIG. 4, separating themid-polymerization product into a mid-polymer stream and a mid-gasstream may further comprise separating at least one gaseous componentfrom the hydrogen-reduced product stream. In such embodiments,hydrogen-reduced product stream 39 entering the separator 105 maycomprise hydrogen, ethylene, ethane, polymer, isobutane, or combinationsthereof. Mid-gas stream 19 may comprise hydrogen, ethylene; ethane, orcombinations thereof; and mid-polymer stream 17 may comprise polymer,isobutane, or combinations thereof. The amount of hydrogen present inthe mid-gas stream 19 of FIG. 4 may be less than 1% by weight of theamount of hydrogen initially present in the mixture withdrawn from thereactor 104, alternatively, less than 0.5% by weight, alternatively, 0wt % by weight.

In one or more of the embodiments disclosed herein, the separators 105,108, and 126 may be configured to separate a stream (e.g.,mid-polymerization product comprising polyethylene, polymerizationproduct comprising polyethylene, hydrogen-reduced product comprisingpolyethylene) into gases, liquids, solids, or combinations thereof. Theproduct streams 12, 15, and 39 may comprise unreacted, gaseous monomersor optional comonomers (e.g., unreacted ethylene monomers, unreactedbutene-1 monomers), gaseous waste products, and/or gaseous contaminants.In embodiments as illustrated in FIG. 4, mid-polymerization productstream 15 may comprise hydrogen. In embodiments as illustrated in FIGS.1-2, polymerization product stream 12 may comprise hydrogen. As usedherein, an “unreacted monomer,” for example, ethylene; refers to amonomer that was introduced into a polymerization reactor during apolymerization reaction but was not incorporated into a polymer. As usedherein, an “unreacted comonomer,” for example, butene-1, refers to acomonomer that was introduced into a polymerization reactor during apolymerization reaction but was not incorporated into a polymer.

In an embodiment, the separators 105, 108, and/or 126 may comprise avapor-liquid separator. Suitable examples of such a separator mayinclude a distillation column, a flash tank, a filter, a membrane, areactor, an absorbent, an adsorbent, a molecular sieve, or combinationsthereof. In an embodiment, the separator comprises a flash tank. Notseeking to be bound by theory, such a flash tank may comprise a vesselconfigured to vaporize and/or remove low vapor pressure components froma high temperature and/or high pressure fluid. The separators 105, 108,and/or 126 may be configured such that an incoming stream may beseparated into a liquid stream (e.g., a condensate stream) and a gas(e.g., vapor) stream. The liquid or condensate stream may comprise areaction product (e.g., polyethylene, often referred to as “polymerfluff”). The gas or vapor stream may comprise volatile solvents,gaseous, unreacted monomers and/or optional comonomers, waste gases(secondary reaction products, such as contaminants and the like), orcombinations thereof. The separators 105, 108, and 126 may be configuredsuch that the feed stream is flashed by heat, pressure reduction, orboth such that the enthalpy of the stream is increased. This may beaccomplished via a heater, a flashline heater, various other operationscommonly known in the art, or combinations thereof. For example, a flashline heater comprising a double pipe may exchange heat by hot water orsteam. Such a flashline heater may increase the temperature of thestream while reducing its pressure.

In one or more embodiments, separating the polymerization product into apolymer stream and a gas stream or separating the mid-polymerizationproduct into a mid-polymer stream and a mid-gas stream may comprisedistilling, vaporizing, flashing, filtering, membrane screening,absorbing, adsorbing, or combinations thereof, the polymerizationproduct. In the embodiments illustrated in FIGS. 1-2, separating thepolymerization product into a polymer stream and a gas stream yields agas stream 18 and a polymer stream 14. In the embodiments illustrated inFIGS. 3-5, separating the mid-polymerization product into a mid-polymerstream and a mid-gas stream yields a mid-gas stream 19 and a mid-polymerstream 17.

In one or more one or more of the embodiments disclosed herein,processing the polymer stream (e.g., at block 64) comprises any suitableprocess or series of processes configured to produce a polymer productas may be suitable for commercial or industrial usage, storage,transportation, further processing, or combinations thereof.

In embodiments as illustrated by FIGS. 1-2, processing the polymerstream may comprise routing the polymer stream 14 to the processor 110.The processor 110 may be configured for the performance of a suitableprocessing means, non-limiting examples of which include cooling,injection molding, melting, pelletizing, blow molding, extrusionmolding, rotational molding, thermoforming, cast molding, the like, orcombinations thereof. Various additives and modifiers may be added tothe polymer to provide better processing during manufacturing and fordesired properties in the end product. Non-limiting examples of suchadditives may include surface modifiers such as slip agents, antiblocks,tackifiers; antioxidants such as primary and secondary antioxidants;pigments; processing aids such as waxes/oils and fluoroelastomers; andspecial additives such as fire retardants, antistats, scavengers,absorbers, odor enhancers, and degradation agents.

In an embodiment, the processor 110 may be configured to form a suitablepolymer product. Non-limiting examples of suitable polymer products asmay result from such processing include films, powders, pellets, resins,liquids, or any other suitable form as will be appreciated by those ofskill in the art. Such a suitable output may be for use in, forexamples, one or more of various consumer or industrial products. Forexample, the polymer product may be utilized any one or more of variousarticles, including; but not limited to, bottles, drums, toys, householdcontainers, utensils, film products, drums, fuel tanks, pipes,geomembranes, and liners. In a particular embodiment, the processor isconfigured to form pellets for transportation to a consumer productmanufacturer. For example, in the embodiments illustrated in FIGS. 1-2,processing the polymer stream yields a polymer product 16 (e.g.,pelletized polyethylene).

In one or more of the embodiments disclosed herein, treating a gasstream (e.g., at block 81) and treating a mid-gas stream (e.g., at block91) may comprise any suitable process or reaction for removing oxygen,oxygenated compounds, oxidizing compounds, or combinations thereof(cumulatively referred to herein as “oxygen”) from the gas stream.Suitable processes or reactions will be appreciated by those of skill inthe art viewing this disclosure. Non-limiting examples of suitableprocesses for removing oxygen include various catalyzed reactions,contacting with a chemical species known to react with oxygen,filtering, absorbing, adsorbing, heating; cooling; or combinationsthereof.

In embodiments as illustrated by FIG. 2, treating the gas stream maycomprise routing the gas stream 18 to the deoxygenator 118. Inembodiments as illustrated by FIG. 5, treating the mid-gas stream maycomprise routing the mid-gas stream 19 to the deoxygenator 118.

In one or more of the embodiments disclosed herein, the deoxygenator 118may comprise a device or apparatus configured for the removal oxygen,from a gas stream. Non-limiting examples of a suitable deoxygenatorinclude various reactors (e.g., a fluidized bed reactor or a fixed bed),a filter, or combinations thereof. A suitable deoxygenator 118 may beconfigured to reduce, prevent, or exclude compounds and/or elements(e.g., oxygen) that may have the effect of poisoning an absorptionsolvent from reaching the absorption reactor (e.g., as will be disclosedherein).

In the embodiments illustrated by FIG. 2, treating the gas stream yieldsa treated gas stream 26 being substantially free of oxygen. In theembodiments illustrated by FIG. 5, treating the mid-gas stream yields atreated gas stream 41 being substantially free of oxygen. As used herein“substantially free of oxygen” refers to a fluid stream comprising nomore than least about 5% oxygen, alternatively, no more than about 1%oxygen, alternatively, no more than about 0.1% oxygen, alternatively, nomore than about 0.01% oxygen by total weight of the stream.

In one or more one or more of the embodiments disclosed herein,separating at least one gaseous component from the gas stream and/or thetreated gas stream, collectively referred to as a gas stream, (e.g., atblock 65, 65′, 75, or 75′) generally comprises any suitable method ofselectively separating at least a first chemical component or compoundfrom a stream comprising the first chemical component or compound andone or more other chemical components, compounds, or the like. Invarious embodiments, the gaseous component separated from the gas streammay comprise one or more hydrocarbons. Non-limiting examples of suchhydrocarbons include alkanes (e.g., ethane, butane, isobutane, hexane,or combinations thereof) and alkenes or olefin monomers (e.g., ethylene,hexane, or combinations thereof) or optional comonomers (e.g.,butene-1). In an embodiment, the gaseous component separated from thegas stream may comprise an unreacted hydrocarbon monomer, e.g.,ethylene. Optionally, the gaseous component separated from the gasstream may comprise an unreacted hydrocarbon comonomer, e.g., propene.In an embodiment, the gaseous component separated from the gas streammay comprise an unreacted hydrocarbon monomer (e.g., ethylene, alone orin combination with other hydrocarbons, such as, ethane, isobutane,hexane, or combinations thereof), or optionally, hydrocarbon comonomer(e.g., propene, alone or in combination with other hydrocarbons, suchas, isobutane, hexane, or combinations thereof). In an embodiment, thegaseous component separated from the gas stream may comprise ethylene,alone or in combination with isobutane. In an embodiment, capturingisobutane may result in a savings of the cost of the captured isobutaneand reduce the presence of isobutane in flare emissions. Non-limitingexamples of suitable separating means include distilling, vaporizing,flashing, filtering, membrane screening, absorbing, adsorbing, molecularweight exclusion, size exclusion, polarity-based separation, orcombinations thereof.

In an embodiment, separating at least one gaseous component from the gasstream may comprise distilling a gas stream (e.g., gas stream 18 of FIG.1, treated gas stream 26 of FIG. 2) in one step so as to allow at leastone gaseous component to separate from other gaseous componentsaccording to temperature(s) of boiling. In such an embodiment,separating at least one gaseous component from the gas stream maycomprise distilling a gas stream into a light hydrocarbon streamcomprising ethylene, ethane, optionally hydrogen, or combinationsthereof. In such an embodiment, separating at least one gaseouscomponent from the gas stream may comprise collecting hexane, hexene,optionally isobutane, or combinations thereof in a distillation bottomsstream. In an additional and/or alternative embodiment, separating atleast one gaseous component from the gas stream may comprise collectingisobutane from a side stream of a distillation column.

In the embodiment of the system 100 shown in FIG. 1, distillation column122 may be configured to separate at least one gaseous component bydistillation. Gas stream 18 may be communicated to distillation column122, and gas stream 18 may comprise the non-solid components ofpolymerization product stream 12 in the vapor phase (e.g., nitrogen,methane, ethylene, ethane, propylene, propane, butane, isobutane,pentane, hexane, hexene-1, heavier hydrocarbons, or combinationsthereof). Gas stream 18 may optionally comprise hydrogen, which may beremoved in separators between two polymerization reactors or byhydrogenation catalyst in the polymerization reactor(s), for example.The at least one gaseous component may be emitted from the distillationcolumn 122 in light hydrocarbon stream 25, and the other gaseouscomponents may be emitted from the distillation column 122 indistillation bottoms stream 23. The at least one gaseous componentemitted from distillation column 122 in light hydrocarbon stream 25 ofFIG. 1 may comprise ethylene and may further comprise other light gases(e.g., ethylene, ethane, methane, carbon dioxide, nitrogen, hydrogen, orcombinations thereof). For example, ethylene may be present in lighthydrocarbon stream 25 in an amount from about 50% to about 99% by totalweight of the light hydrocarbon stream 25, alternatively from about 60%to about 98%, alternatively, from about 70% to about 95%. The othergaseous components emitted from the distillation column 122 indistillation bottoms stream 23 may comprise propylene, propane, butane,isobutane, pentane, hexane, hexene-1, heavier hydrocarbons, orcombinations thereof. In an embodiment, the distillation bottoms stream23 may be free of olefins, alternatively, substantially free of olefins,alternatively, essentially free of olefins. For example, olefins may bepresent in distillation bottoms stream 23 in an amount less than about1.0% by total weight of the distillation bottoms stream 23,alternatively, less than about 0.5%, alternatively, less than about0.1%. In an embodiment, side stream 27 comprising isobutane may beemitted from the distillation column 122 in side stream 27.

In embodiments as illustrated in FIG. 1, side stream 27 or at least aportion of distillation bottoms stream 23 may be recycled. Recycling theside stream 27 or at least a portion of distillation bottoms stream 23may comprise routing, for example, via a suitable pump or compressor,the side stream 27 or at least a portion of distillation bottoms stream23 back to and/or introducing the side stream 27 or at least a portionof distillation bottoms stream 23 into the PEP system 100, for example,for reuse in a polymerization reaction. In an embodiment, side stream 27or at least a portion of distillation bottoms stream 23 may be combinedwith various other components (catalysts, cocatalysts, etc.) to form acatalyst slurry that may be introduced into one or more of reactors 104,106. Not intending to be bound by theory, because the side stream 27 orat least a portion of distillation bottoms stream 23 may comprise anolefin-free isobutane stream (alternatively, a substantiallyolefin-free, as disclosed above), the side stream 27 or at least aportion of distillation bottoms stream 23 may be mixed with catalyticcomponents (e.g., catalysts, cocatalysts, etc.) without the risk ofunintended polymerization reactions (e.g., polymerization prior tointroduction into the one or more reactors). As such, the side stream 27or at least a portion of distillation bottoms stream 23 may serve as asource of olefin-free isobutane for a polymerization reaction. Recyclingthe side stream 27 or at least a portion of distillation bottoms stream23 (comprising olefin-free isobutane) may provide an efficient and/orcost-effective means of supplying isobutane for operation of thepolymerization reaction process. In an alternative embodiment, sidestream 27 or at least a portion of distillation bottoms stream 23 may berouted to storage for subsequent use in a polymerization reaction oremployed in any other suitable process.

In an embodiment, at least a portion of the side stream 27 or at least aportion of distillation bottoms stream 23 may be returned to thedistillation column 122. For example, side stream 27 or at least aportion of distillation bottoms stream 23 may be routed via a reboilerto the distillation column 122 for additional processing.

The distillation column 122 may be configured and/or sized provide forseparation of a suitable volume of gases (e.g., the light hydrocarbonstream 25 of FIG. 1). For example, the distillation column 122 may beoperated at a temperature in a range of from about 50° C. to about 20°C., alternatively, from about 40° C. to about 10° C., alternatively,from about 30 to about 5° C., and a pressure in a range of from about14.7 psia to about 529.7 psia, alternatively, from about 15.7 psia toabout 348 psia, alternatively, from about 85 psia to about 290 psia. Thedistillation column 122 may be configured and/or sized to provide forseparation of a suitable volume of gas stream 18 or a treated gas stream(e.g., stream 26 of FIG. 2). As will be appreciated by one of skill inthe art, the gas stream 18 (optionally, a treated gas stream) may remainand/or reside within distillation column 122 for any suitable amount oftime as may be necessary to provide sufficient separation of thecomponents of gas stream 18 (optionally, a treated gas stream). In anembodiment, distillation column 122 may be provided with at least twooutlets.

In an embodiment, the distillation column 122 may be configured and/oroperated such that each of light hydrocarbon stream 25 of FIG. 1,optional side stream 27, and the distillation bottoms stream 23 maycomprise a desired portion, part, or subset of components of the gasstream 18 (optionally, treated gas stream). For example, as will beappreciated by one of skill in the art with the aid of this disclosure,the location of a particular stream inlet or outlet, the operatingparameters of the distillation column 122, the composition of the gasstream 18 (optionally, treated gas stream), or combinations thereof maybe manipulated such that a given stream may comprise a particular one ormore components of the gas stream 18 (optionally, treated gas stream).

In an alternative embodiment, separating at least one gaseous componentfrom the gas stream may comprise distilling a gas stream (e.g., gasstream 18 or treated gas stream 26) in two steps, so as to allow atleast one gaseous component to separate from other gaseous componentsaccording to temperature(s) of boiling in a first separation, and so asto allow at least another gaseous component to separate from the othergaseous components according to temperature(s) of boiling in a secondseparation. In such an embodiment, separating at least one gaseouscomponent from the gas stream in a first separation may comprisedistilling the gas stream to form an intermediate hydrocarbon streamcomprising ethylene, ethane, hydrogen, isobutane, or combinationsthereof. In such an embodiment, separating at least one gaseouscomponent from the gas stream may comprise collecting hexane, optionallyhexene, or combinations thereof in a distillation bottoms stream of adistillation column of the first separation. Additionally, separating atleast one gaseous component from the gas stream in a second separationmay comprise distilling ethylene, ethane, optionally hydrogen, orcombinations thereof from the intermediate hydrocarbon stream;collecting hexane, optionally hexene, optionally isobutane, orcombinations thereof in a distillation bottoms stream of the secondseparation; and optionally collecting isobutane from a side stream ofthe distillation column of the second separation.

In the embodiment of the system 200 shown in FIG. 2, distillationcolumns 126 and 124 may be configured to separate at least one gaseouscomponent from treated gas stream 26 or gas stream 18. Treated gasstream 26 and gas stream 18 may comprise the non-solid components ofpolymerization product stream 12 in the vapor phase (e.g., nitrogen,methane, ethylene, ethane, propylene, propane, butane, isobutane,pentane, hexane, hexene-1, heavier hydrocarbons, or combinationsthereof). Treated gas stream 26 and gas stream 18 may optionallycomprise hydrogen, which may be removed in separators between twopolymerization reactors or by dehydrogenation catalyst in thepolymerization reactor(s), for example. Treated gas stream 26 or gasstream 18 may be distilled to form intermediate hydrocarbon stream 29.Non-distilled components in the distillation column 126 may emit fromthe distillation column 126 in distillation bottoms stream 43. Sidestream 45 may optionally emit from the distillation column 126.

Intermediate hydrocarbon stream 29 may be characterized as comprising,alternatively, comprising substantially, alternatively, consistingessentially of, alternatively, consisting of, C₄ and lighterhydrocarbons (e.g., butane, isobutane, propane, ethane, or methane) andany light gases (e.g., hydrogen or nitrogen). For example, C₄ andlighter hydrocarbons and gases may be present in the intermediatehydrocarbon stream 29 in an amount of from about 80% to about 100% bytotal weight of the intermediate hydrocarbon stream, alternatively fromabout 90% to about 99.999999%, alternatively from about 99% to about99.9999%, alternatively, C₅ and heavier hydrocarbons may be present inthe intermediate hydrocarbon stream 29 in an amount from 0% to about 20%by total weight of the intermediate hydrocarbon stream, alternativelyfrom about 10% to about 0.000001%, alternatively from about 1.0% toabout 0.0001%. Also, for example, at least 90% by weight of the treatedgas stream 26 or gas stream 18 of the C₄ and lighter hydrocarbons andgases may be present in the intermediate hydrocarbon stream 29,alternatively, at least 98%, alternatively, at least 99%.

In an embodiment, distillation bottoms stream 43 may be characterized ascomprising C₆ and heavier components such as alkanes, that is, alkaneslarger than hexane (e.g., heptane and/or other large alkanes). In anembodiment, hydrocarbons other than C₆ and heavier alkanes may bepresent in the distillation bottoms stream 43 in an amount less thanabout 15%, alternatively, less than about 10%, alternatively, less thanabout 5% by total weight of the distillation bottoms stream 43. In anembodiment, the distillation bottoms stream 43 may be directed toadditional processing steps or methods, or alternatively they may bedisposed of, as appropriate. In an embodiment, distillation bottomsstream 43 may be directed to a flare for disposal.

In an embodiment, side stream 45 may be characterized as comprisinghexene. For example, hexene may be present in side stream 45 in anamount of from about 20% to about 98% by total weight of the side stream45, alternatively from about 40% hexene to about 95%, alternatively fromabout 50% hexene to about 95% hexene.

In an embodiment, the side stream 45 may be recycled. In the embodimentof FIG. 2, recycling the side stream 45 may comprise routing, forexample, via a suitable pump or compressor, the side stream 45 back toand/or introducing the side stream 45 into the PEP system 200, forexample, for reuse in a polymerization reaction. Recycling the sidestream 45 (e.g., comprising hexene) may provide an efficient and/orcost-effective means of supplying hexene for operation of thepolymerization reaction process. In an embodiment, the hexene of sidestream 45 may be employed in the polymerization reaction as, forexample, a comonomer in the reaction. In an alternative embodiment, sidestream 45 may be routed to storage for subsequent use in apolymerization reaction or employed in any other suitable process.

In an embodiment, distillation column 126 may be provided with one ormore inlets and at least two outlets. The distillation column 126 may beoperated at a suitable temperature and pressure, for example as may besuitable to achieve separation of the components of the treated gasstream 26 or gas stream 18. For example, the distillation column 126 maybe operated at a temperature in a range of from about 15° C. to about233° C., alternatively, from about 20° C. to about 200° C.,alternatively, from about 20° C. to about 180° C., and/or a pressure ina range of from about 14.7 psi to about 527.9 psi, alternatively, fromabout 15.7 psi to about 348 psi, alternatively, from about 85 psi toabout 290 psi. The distillation column 126 may be configured and/orsized provide for separation of a suitable volume of gases (e.g., theflash gas stream). As will be appreciated by one of skill in the artviewing this disclosure, the treated gas stream 26 or gas stream 18 mayremain and/or reside within distillation column 126 for any suitableamount of time, for example an amount of time as may be necessary toprovide sufficient separation of the components of distillation column126.

In an embodiment, the treated gas stream 26 or gas stream 18 may beintroduced into the distillation column 126 without a compressive step,that is, without compression of the treated gas stream 26 or gas stream18 after it is emitted from the separator 108 and before it isintroduced into the distillation column 126. In another embodiment, thetreated gas stream 26 or gas stream 18 may be introduced into thedistillation column 126 at substantially the same pressure as the outletpressure of separator 108 (e.g., a pressure of from about 14.7 psia toabout 527.9 psia, alternatively, from about 15.7 psia to about 348 psia,alternatively, from about 85 psia to about 290 psia at the outlet of theflash chamber 130). In still another embodiment, the treated gas stream26 or gas stream 18 may be introduced into the distillation column 126without a significant compressive step. In an embodiment, treated gasstream 26 or gas stream 18 may be introduced into distillation column126 at a pressure in a range of from about 25 psi less than the pressureat which the gas stream 18 was emitted from the separator 108 to about25 psi greater than the pressure at which the gas stream 18 was emittedfrom the separator 108, alternatively, from about 15 psi less than thepressure at which the gas stream 18 was emitted from the separator 108to about 15 psi greater than the pressure at which the gas stream 18 wasemitted from the separator 108, alternatively, from about 5 psi lessthan the pressure at which the gas stream 18 was emitted from theseparator 108 to about 5 psi greater than the pressure at which the gasstream 18 was emitted from the separator 108. In an embodiment, thetreated gas stream 26 or gas stream 18 may be introduced into thedistillation column 126 at a pressure in a range of from about 14.7 psiato about 527.8 psia, alternatively, from about 15.7 psia to about 348psia, from about 85 psia to about 290 psia.

In an embodiment, the distillation column 126 may be configured and/oroperated such that each of the intermediate hydrocarbon stream 29, thedistillation bottoms stream 43, and an optional side stream 45 maycomprise a desired portion, part, or subset of components of the gasstream 18 or treated gas stream 26. For example, as will be appreciatedby one of skill in the art with the aid of this disclosure, the locationof a particular stream outlet, the operating parameters of thedistillation column 126, the composition of the treated gas stream 26 orgas stream 18, or combinations thereof may be manipulated such that agiven stream may comprise a particular one or more components of thetreated gas stream 26 or gas stream 18.

In the embodiment of the system 200 shown in FIG. 2, the intermediatehydrocarbon stream 29 may be separated in the distillation column 124 toform light hydrocarbon stream 25, distillation bottoms stream 33, andoptionally, side stream 31. Light hydrocarbon stream 25 may compriseethylene, ethane, optionally hydrogen, or combinations thereof.Distillation bottoms stream 33 may comprise isobutane. Side stream 31may comprise isobutane. The isobutane of distillation bottoms stream 33may comprise a different grade of isobutane than side stream 31. Forexample, distillation bottoms stream 33 may comprise isobutane that issubstantially free of olefins, and side stream 31 may comprise a recycleisobutane which may include olefins.

At least one gaseous component may be emitted from the distillationcolumn 124 in light hydrocarbon stream 25, and the other gaseouscomponents may be emitted from the distillation column 124 indistillation bottoms stream 33. The at least one gaseous componentemitted from distillation column 124 in light hydrocarbon stream 25 ofFIG. 2 may comprise ethylene and may further comprise other light gases(e.g., ethylene, ethane, methane, carbon dioxide, nitrogen, hydrogen, orcombinations thereof). For example, ethylene may be present in lighthydrocarbon stream 25 in an amount from about 50% to about 99% by totalweight of the light hydrocarbon stream 25, alternatively from about 60%to about 98%, alternatively, from about 70% to about 95%.

The other gaseous components emitted from the distillation column 124 indistillation bottoms stream 33 may comprise propylene, propane, butane,isobutane, pentane, hexane, hexene-1, heavier hydrocarbons, orcombinations thereof. In an embodiment, the distillation bottoms stream33 may be free of olefins, alternatively, substantially free of olefins,alternatively, essentially free of olefins. For example, olefins may bepresent in distillation bottoms stream 33 in an amount less than about1.0% by total weight of the distillation bottoms stream 33,alternatively, less than about 0.5%, alternatively, less than about0.1%. In an embodiment, side stream 31 comprising, alternatively,consisting of, isobutane may be emitted from the distillation column 124in side stream 31.

In an embodiment, side stream 31 or at least a portion of distillationbottoms stream 33 may be recycled. Recycling the side stream 31 or atleast a portion of distillation bottoms stream 33 may comprise routing,for example, via a suitable pump or compressor, the side stream 31 or atleast a portion of distillation bottoms stream 33 back to and/orintroducing the side stream 31 or at least a portion of distillationbottoms stream 33 into the PEP system 200, for example, for reuse in apolymerization reaction. In an embodiment, side stream 31 or at least aportion of distillation bottoms stream 33 may be combined with variousother components (catalysts, cocatalysts, etc.) to form a catalystslurry that may be introduced into one or more of reactors 104, 106. Notintending to be bound by theory, because at least a portion ofdistillation bottoms stream 33 may be free of olefins and may compriseisobutane, the distillation bottoms stream 33 may be mixed withcatalytic components (e.g., catalysts, cocatalysts, etc.) without therisk of unintended polymerization reactions (e.g., polymerization priorto introduction into the one or more reactors). As such, at least aportion of distillation bottoms stream 33 may serve as a source ofolefin-free isobutane for a polymerization reaction. Recycling the sidestream 31 or at least a portion of distillation bottoms stream 33 mayprovide an efficient and/or cost-effective means of supplying isobutanefor operation of the polymerization reaction process. In an alternativeembodiment, side stream 31 or at least a portion of distillation bottomsstream 33 may be routed to storage for subsequent use in apolymerization reaction or employed in any other suitable process.

In an embodiment, at least a portion of the side stream 31 or at least aportion of distillation bottoms stream 33 may be returned to thedistillation column 124. For example, side stream 31 or at least aportion of distillation bottoms stream 33 may be routed via a reboilerto the distillation column 124 for additional processing.

The distillation column 124 may be configured and/or sized provide forseparation of a suitable volume of gases (e.g., the light hydrocarbonstream 25 of FIG. 2). For example, the distillation column 124 may beoperated at a temperature in a range of from about 50° C. to about 20°C., alternatively, from about 40° C. to about 10° C., alternatively,from about 30 to about 5° C., and a pressure in a range of from about14.7 psia to about 529.7 psia, alternatively, from about 15.7 psia toabout 348 psia, alternatively, from about 85 psia to about 290 psia. Thedistillation column 124 may be configured and/or sized to provide forseparation of a suitable volume of gas stream 18 or a treated gas stream26. As will be appreciated by one of skill in the art, the treated gasstream 26 or gas stream 18 may remain and/or reside within distillationcolumn 124 for any suitable amount of time as may be necessary toprovide sufficient separation of the components of treated gas stream 26or gas stream 18. In an embodiment, distillation column 124 may beprovided with at least two outlets.

In an embodiment, the distillation column 124 may be configured and/oroperated such that each of light hydrocarbon stream 25 of FIG. 2 and thedistillation bottoms stream 33 may comprise a desired portion, part, orsubset of components of the treated gas stream 26 or gas stream 18. Forexample, as will be appreciated by one of skill in the art with the aidof this disclosure, the location of a particular stream inlet or outlet,the operating parameters of the distillation column 124, the compositionof the treated gas stream 26 or gas stream 18, or combinations thereofmay be manipulated such that a given stream may comprise a particularone or more components of the treated gas stream 26 or gas stream 18.

In an alternative and/or additional embodiment, separating at least onegaseous component from the gas stream may comprise contacting the gasstream with the absorbent (e.g., an absorption solvent system, asdisclosed herein), for example, so as to allow the gaseous component tobe absorbed by the absorbent. In such an embodiment, separating at leastone gaseous component from the gas stream comprises selectivelyabsorbing the at least one gaseous component from a gas stream. In suchan embodiment, absorbing the at least one gaseous component from the gasstream generally comprises contacting the gas stream with a suitableabsorbent, allowing the at least one component to be absorbed by theabsorbent, and, optionally, removing a waste stream comprisingunabsorbed gases. In an additional embodiment, separating at least onegaseous component from the gas stream may further comprise liberatingthe absorbed gaseous component from the absorbent.

In an embodiment, contacting the gas stream with the absorbent maycomprise any suitable means of ensuring sufficient contact between thegas stream and the absorbent. Non-limiting examples of suitable means bywhich to provide sufficient contact between the gas stream and theabsorbent include the use of various reactor systems, such as thosedisclosed above (e.g., an absorption column or sparged or mixed tank).Not intending to limited by theory, a suitable reactor system may ensurecontact between a two or more gaseous, liquid, and or solid compositionsby agitating or mixing the two components in the presence of each other,circulating, dispersing, or diffusing a first composition through orwithin a second composition, or various other techniques known to thoseof skill in the art. In an embodiment, the gas stream and the absorbentmay be brought into contact in a suitable ratio. Such a suitable ratioof gas stream to absorbent may be in a range of from about 1,000lb/hr:1000 gpm to about 2,500 lb/hr:25 gpm, alternatively, from about1000 lb/hr:250 gpm to about 2500 lb/hr:100 gpm, alternatively, about1875 lbs/hr:250 gpm.

In an embodiment as illustrated by FIGS. 1-5, separating at least onegaseous component from the gas stream (e.g., gas stream 18 of FIG. 1 ortreated gas stream 26 of FIG. 2 or mid-gas stream 19 of FIGS. 3-5) maycomprise routing the gas stream to the absorption reactor 116. In one ormore of the embodiments disclosed herein, the absorption reactor 116 maycomprise a reactor configured to selectively absorb at least a firstchemical component or compound from a stream comprising the firstchemical component or compound and one or more other chemicalcomponents, compounds, or the like. Non-limiting examples of suitableabsorption reactors and/or absorption reactor configurations include anabsorption (distillation) tower, a pressure-swing absorption (PSA)configuration, a sparger tank, an agitation reactor, one or morecompressors, one or more recycle pumps, or combinations thereof.

In an embodiment, the absorption reactor may be configured to dissipatea gas within a liquid (e.g., by bubbling the gas through the liquid).For example, in an embodiment, the absorption reactor 116 may include asolvent circulation system configured to circulate solvent through theabsorption reactor 116. The solvent circulation flow rate may bedetermined by the operating conditions of the absorption system, as isdisclosed herein below. In an embodiment, the absorption reactor 116 maycomprise and/or be in fluid communication with one or more pumpsconfigured to recirculate solvent via and/or within the absorptionreactor 116. In an additional and/or alternative embodiment, theabsorption reactor 116 may comprise a packed bed or column configured tomaintain smaller bubble sizes of the gas being dissipated within theliquid), for example, so as to maintain a relatively large surface areaof contact between the gas and the liquid, for example, so as tomaintain an efficiency of mass transfer and/or absorption of the gasinto the liquid. In an embodiment, the packing material of the packedbed or column may comprise a polymeric material, metallic material, orcombinations thereof. In an embodiment, the absorption reactor 116 mayhave multiple packed beds or columns. In an embodiment, only a sectionof the absorption reactor 116 may have a packing material. In anembodiment, the packing material of a packed absorption reactor 116 mayhave a random packing or may have a structured packing. An example of asuitable absorption reactor is illustrated in the Gas ProcessorsAssociation, “Engineering Data Book” 10^(th) ed. at FIG. 19-16.

In an embodiment where the absorption reactor 116 comprises a solventreactor, the absorption reactor may comprise a suitable absorptionsolvent system, as will be disclosed herein. Such an absorption reactor116 may be configured to retain the absorption solvent system. Forexample, the absorption solvent system may be retained within thereactor as a liquid, as a fixed bed, or as a fluidized bed.

In an embodiment, a suitable absorption solvent system may be capable ofreversibly complexing with the ethylene and/or isobutane. Such anabsorption solvent system may generally comprise a complexing agent anda solvent. In an embodiment, an absorption solvent system may becharacterized as having a selectivity of ethylene to ethane whereethylene and ethane are present at the same partial pressure of about40:1 at approximately 14 psi, about 12:1 at approximately 20 psi, about6:1 at approximately 40 psi, and about 3:1 at approximately 180 psipartial pressure. In an embodiment, the solvent system may be furthercharacterized as having a high contaminant tolerance and as exhibitinghigh stability at increased and/or fluctuating temperatures and/orpressures, or combinations thereof.

In an embodiment, the complexing agent may comprise a metallic salt. Insuch an embodiment, the metallic salt may comprise a salt of one or moretransition metals and a weakly-ionic halogen. Non-limiting examples ofsuitable transition metals include silver, gold, copper, platinum,palladium, or nickel. Non-limiting example of suitable weakly-ionichalogens include chlorine and bromine. In an embodiment, a suitabletransition metal salt may be characterized as having a high specificityfor olefins. Non-limiting examples of suitable transition metal-halogensalts include silver chloride (AgCl) and copper chloride (CuCl). In aparticular embodiment, the salt employed in the absorption solventsystem comprises CuCl. Not seeking to be bound by theory, such ametallic salt may interact with the double carbon bonds of olefins(e.g., ethylene).

In an embodiment, the complexing agent may comprise a copper (I)carboxylate. In such an embodiment, suitable copper (I) carboxylates maycomprise salts of copper (I) and mono-, di-, and/or tri-carboxylic acidscontaining 1-20 carbon atoms. The carboxylic acid component of the saltmay comprise an aliphatic constituent, a cyclic constituent, an arylconstituent, or combinations thereof. Other suitable examples of copper(I) carboxylates include Cu(I) formate, Cu(I) acetate, Cu(I) propionate,Cu(I) butyrate, Cu(I) pentanoate, Cu(I) hexanoate, Cu(I) octanoate,Cu(I) decanoate, Cu(I) 2-ethyl-hexoate, Cu(I) hexadecanoate, Cu(I)tetradecanoate, Cu(I) methyl formate, COO ethyl acetate, Cu(I) n-propylacetate, Cu(I) n-butyl acetate, Cu(I) ethyl propanoate, Cu(I) octoate,Cu(I) benzoate, Cu(I) p-t-butyl benzoate, and the like. In an additionalembodiment, the complexing agent may comprise an adduct of a copper (I)carboxylate, for example, as disclosed herein, and boron trifluoride(BF₃).

In an additional and/or alternative embodiment, the complexing agent maycomprise a copper (I) sulfonate. Non-limiting examples of suitablecopper (I) sulfonates include the copper (I) salts of sulfonic acidshaving 4 to 22 carbon atoms. The sulfonic acid component of the salt maycomprise an aliphatic constituent, a cyclic constituent, an arylconstituent, or combinations thereof. The aliphatic sulfonic acids canbe straight chain or branched. Examples of suitable aliphatic sulfonicacids include, but are not limited to, n-butanesulfonic acid,2-ethyl-1-hexanesulfonic acid, 2-methylnonanesulfonic acid,dodecanesulfonic acid, 2-ethyl-5-n-pentyltridecanesulfonic acid,n-eicosanesulfonic acid, and the like. Examples of suitable aromaticsulfonic acids include benzenesulfonic acid, alkylbenzenesulfonic acidswherein the alkyl member contains from 1 to 16 carbon atoms, such asp-toluenesulfonic acid, dodecylbenzenesulfonic acid (o-, m-, and p-),p-hexadecylbenzenesulfonic acid, and the like, naphthalenesulfonic acid,phenolsulfonic acid, naphthol sulfonic acids, and halobenzenesulfonicacids, such as p-chlorobenzenesulfonic acid, p-bromobenzenesulfonicacid, and the like.

In an embodiment the complexing agent may further comprise a hinderedolefin. For example, the complexing agent may comprise such a hinderedolefin in an embodiment wherein the complexing agent forms a coppercomplex with insufficient solubility. An example of such a hinderedolefin is a propylene tetramer (i.e. dodecene). Not intending to bebound by theory, the hindered olefin may increase the solubility of thecopper complex while being easily displaced by ethylene.

In various embodiments, the complexing agent may comprise one or more ofthe complexing agents disclosed in U.S. Pat. Nos. 5,104,570; 5,191,153;5,259,986; and 5,523,512, each of which is incorporated by reference inits entirety.

In an embodiment, the solvent may comprise an amine or an amine complex,an aromatic hydrocarbon, an olefin, or combinations thereof.Non-limiting examples of solvent amines include pyridine, benzylamine,and aniline. For example, the amine may comprise an aniline(phenylamine, aminobenzene); alternatively, aniline combined withdimethylformamide (DMF), and in embodiments, aniline andN-methylpyrrolidone (NMP). In an embodiment where the solvent comprisesan aromatic hydrocarbon, the aromatic hydrocarbon may comprise anunsubstituted or alkyl substituted aryl groups. In such an embodiment,the aromatic hydrocarbon may be in the liquid phase under normal,ambient conditions. Suitable non-limiting examples include toluene,xylene, and the like. In embodiments where the solvent comprises anolefin, non-limiting examples include olefins having 10 to 16 carbonatoms. For example, the olefin may comprise propylene tetramer,dodecene, tetradecene, hexadecene, or combinations thereof.

In an embodiment, the solvent may be characterized as aprotic, that is,as not including a dissociable hydrogen atom. Not intending to be boundby theory, a dissociable hydrogen solvent may result in thehydrogenation of the double bond between carbons in an olefin such asethylene. Further, the solvent may be characterized as polar, as havinga slight polarity, or as having unidirectional, electric charge. Notintending to be bound by theory, a polar solvent may interact with andat least partially solubilize the salt.

In an embodiment, the solvent may be characterized as a liquid producedindustrially in relatively high volumes, having a relatively low cost,being easily transportable, or combinations thereof. The solvent may befurther characterized as capable of retaining a complexed metal salt orretaining a weakly ionic metal salt despite fluctuations in temperatureand/or pressure.

In an embodiment, the absorption solvent system may comprise copperchloride, aniline, and dimethylformamide (CuCl/aniline/DMF). In analternative embodiment, the absorption solvent system may comprisecopper chloride, aniline, and N-methylpyrrolidone (CuCl/aniline/NMP). Insuch an embodiment, a CuCl/aniline/NMP solvent system may becharacterized as having increased volatile stability at lower pressuresand higher temperatures. In alternative embodiments, the absorptionsolvent system may comprise copper (I) carboxylate and an aromaticsolvent such as toluene or xylene. In alternative embodiments, theabsorption solvent system may comprise copper (I) sulfonate and anaromatic solvent such as toluene or xylene. In alternative embodiments,the absorption solvent system may comprise an adduct of copper (I)carboxylate and BF₃ in an aromatic solvent such as toluene or xylene.

In an embodiment, the absorption solvent system may comprise copper (I)2-ethyl-hexanoate and propylene tetramer. In an embodiment, theabsorption solvent system may comprise copper (I) 2-ethyl-hexanoate anddodecene. In an embodiment, the absorption solvent system may comprisecopper (I) hexadecanoate and hexadecene. In an embodiment, theabsorption solvent system may comprise copper (I) tetradecanoate andtetradecene.

In an embodiment, allowing the at least one component to be absorbed bythe absorbent may comprise allowing the at least one component to becomereversibly bound, linked, bonded or combinations thereof to theabsorbent or a portion thereof, for example, via the formation ofvarious links, bonds, attractions, complexes, or combinations thereof.For example, in an embodiment where the absorbent comprises anabsorption solvent system (e.g., a CuCl/aniline/DMF solvent system or aCuCl/aniline/NMP solvent system), allowing absorption of the at leastone component may comprise allowing a complex to form between theabsorbent and the at least one component, referred to as an absorbedcomponent complex (e.g., an absorbed ethylene complex).

Allowing absorption of the at least one component may further compriseproviding and/or maintaining a suitable pressure of the environment inwhich the gas stream and absorbent are brought into contact, providingand/or maintaining a suitable partial pressure of a gas, providingand/or maintaining a suitable temperature in the environment in whichthe gas stream and absorbent are brought into contact, catalyzing theabsorption, or combinations thereof. Not intending to be bound bytheory, the absorption of the at least one component by the absorbentmay be improved at a suitable temperature and/or pressure.

In an embodiment, the absorption reactor 116 may be capable ofselectively inducing thermal and/or pressure fluctuations, variations,or cycles. In an embodiment, the absorption reactor 116 may beconfigured to selectively absorb and/or induce the absorption of anunreacted ethylene monomer (and optionally, comonomer) from acomposition comprising various other gases (e.g., ethane, optionallyhydrogen). In another embodiment, the absorption reactor 116 may beconfigured to selectively absorb and/or induce the absorption of butane,particularly, isobutane, from a composition comprising various othergases. In still another embodiment, the absorption reactor 116 may beconfigured to selectively absorb both unreacted ethylene and butane,particularly, isobutane, from a composition comprising various othergases ethane, optionally hydrogen).

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature, for example, as may bedependent upon the phase in which the absorption reactor operates at agiven time. For example, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature, for example, for the purposeof increasing absorption of a desired chemical species, decreasingabsorption of a desired chemical species, flashing an unabsorbed gasfrom the reactor 116, recovering unreacted ethylene from the absorptionreactor 116, regenerating absorbent in the absorption reactor 116, orcombinations thereof. In an embodiment, such a suitable temperature maybe in a range of from about 40° F. to about 110° F., alternatively, fromabout 40° F. to about 60° F., alternatively, from about 45° F. to about55° F., alternatively, from about 50° F. to about 55° F., alternativelyabout 50° F. For example, it has been found the operating temperature ofthe absorption reactor 116 (and absorption solvent system) in atemperature range of from about 40° F. to about 110° F., alternatively,from about 40° F. to about 60° F., alternatively about 50° F. may yieldan unexpected increase in the absorption of ethylene relative to theabsorption of ethane. Not intending to be bound by theory, one skilledin the art will appreciate (for example, based on partial pressureconcepts from Raoult's law) the expectation for solubility of ethyleneand ethane in an absorbent solvent to increase at decreasingtemperatures. However, contrary to such expectations, it has been foundthat the amount of ethylene absorbed in the absorbent solvent and/or theabsorbent solvent system of the disclosed embodiments decreases as thetemperature decreases below 50° F. Because of this unexpectedphenomenon, absorption of ethylene may be greatest for temperatures in arange of from about 40° F. to about 110° F., alternatively, in a rangeof from about 40° F. to about 60° F., alternatively, at a temperature ofabout 50° F. FIG. 11 is graph showing the solubility at varyingtemperatures for ethylene and ethane in a copper chloride, aniline, NMPabsorbent solvent system. The graph illustrates the expected solubilitytrend of ethane and the unexpected solubility trend of ethylene acrossthe temperatures discussed above.

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable temperature in a range from about 40° F.to about 110° F. during absorption of one or more components of the gasstream (e.g., ethylene and/or isobutane). As disclosed above, it hasbeen found that ethylene solubility is unexpectedly greatest attemperature in a range of from about 40° F. to about 60° F. In anembodiment, the absorption reactor 116 may be operated at a temperatureof from about 40° F. to about 60° F., alternatively a temperature ofabout 50° F. during absorption of ethylene and/or isobutene from a gasstream. In an alternative embodiment, the absorption reactor may beoperated at a temperature of from about 60° F. to about 110° F., or fromabout 70° F. to about 90° F. during absorption of ethylene and/orisobutene from a gas stream. For example, such absorption temperaturesof the absorption reactor 116 may be suitable as an economic alternativeto operating at a lower temperature (which may require energyexpenditure with cooling, for example). For example, operating anabsorption reactor, like absorption reactor 116, at temperatures in arange of from about 60° F. to about 110° F., or from about 70° F. toabout 90° F. may require less energy, which may create a cost savings,by allowing the absorption reactor to be operated at the ambienttemperature of a given geographic location.

In an embodiment, the absorption reactor 116 may be configured toprovide or maintain a suitable pressure during operation. Such asuitable pressure may be in a range of from about 5 psig to about 500psig, alternatively, from about 50 psig to about 450 psig,alternatively, from about 75 psig to about 400 psig. In an additionalembodiment, the absorption reactor 116 may be configured to provide ormaintain a suitable partial pressure of ethylene during operation. Sucha suitable ethylene partial pressure may be in a range of from about 1psia to about 400 psia, alternatively, from about 30 psia to about 200psia, alternatively, from about 40 psia to about 250 psia,alternatively, from about 40 psia to about 75 psia, alternatively, fromabout 40 psig to about 60 psig, alternatively about 40 psig,alternatively, about 60 psig. Not intending to be bound by theory,pressurizing the absorption reactor 116 may facilitate absorption ofethylene and/or the formation of a complex of ethylene and theabsorption solvent system (e.g., the CuCl/aniline/NMP system). Also, notintending to be bound by theory, the selectivity of the absorptionsolvent system for ethylene may increase with a decrease in the pressureof the absorption reactor.

In an embodiment, the absorption reactor 116 may be configured for batchand/or continuous processes. For example, in an embodiment, a PEP systemmay comprise two or more absorption reactors (e.g., such as absorptionreactor 116), each of which may be configured for batch operation. Forexample, by employing two or more absorption reactors, such a system maybe configured to allow for continuous operation by absorbing a componentof a gas stream into a “first batch” in the first absorption reactorwhile a “second batch” is prepared for absorption in the secondabsorption reactor. As such, by cycling between two or more suitablereactors, a system may operate continuously.

For example, in an embodiment two or more absorption reactors (e.g., anabsorption reactor system) may be configured for pressure swingabsorption (PSA) of ethylene using a liquid solvent, for example, theabsorption solvent system or absorption solvent as disclosed herein. Insuch an embodiment, the absorption reactor 116 may include two or moreabsorption reactors configured for PSA (e.g., an absorption reactorsystem). FIG. 10, shows an absorption reactor system 1000 with fourabsorption reactors 1010, 1020, 1030, and 1040 configured for PSA.Although the embodiment of FIG. 10 illustrates four absorption reactors(e.g., absorption reactors 1010, 1020, 1030, and 1040), one of skill inthe art, upon viewing this disclosure, will recognize that two, three,five, six, seven, eight, or more absorption reactors may be similarlyemployed. In such an embodiment, the each of the absorption reactors maybe configured substantially as disclosed herein. In an embodiment, oneor more of the reactors 1010, 1020, 1030, and 1040 may be connected viaa circulation system (for example, comprising one or more pumps, valves,conduits, and the like) to circulate the liquid solvent in the reactors1010, 1020, 1030, and 1040 during absorption. The absorption reactors1010, 1020, 1030, and 1040 may cycle between an absorption phase (inwhich a gaseous component, such as ethylene and/or isobutane, isabsorbed by the absorption solvent and/or absorption solvent system) anda regeneration phase (in which the absorbed and/or complexed gaseouscomponent is liberated from the absorption solvent system and/or theabsorption solvent system is prepared for reuse, as will be disclosedherein). For example, the reactors 1010, 1020, 1030, and 1040 may becycled between the absorption and regeneration phases (e.g., via one ormore intermediate phases) on a coordinated basis so that not allreactors 1010, 1020, 1030, 1040 are undergoing absorption orregeneration at the same time. In an embodiment where absorptionreactors 1010, 1020, 1030, and 1040 are configured to operate in PSA,the reactors 1010, 1020, 1030, and 1040 serve as both absorbers and asregenerators. In such an embodiment, separate vessels for regenerationmay not be required (e.g., as disclosed herein).

As an example of PSA operation on a coordinated basis, at a given phaseduring such operation, reactor 1010 may operate in the absorption phase,for example, at absorption conditions as disclosed herein. Atsubstantially the same time, reactor 1020 may be pressurized to anintermediate pressure, for example, below that of the absorptionpressure. Also, at substantially the same time, reactor 1030 maydepressurize from an intermediate pressure to a regeneration pressure,and while reactor 1040 may depressurize from an absorption pressure(from previously being in an absorption phase) to an intermediatepressure. Not intending to be bound by theory, depressurization (e.g.,from the absorption pressure to the intermediate pressure and from theintermediate pressure to the regeneration pressure) of each of reactors1010, 1020, 1030, and/or 1040 following absorption may allow theabsorbed gaseous components (e.g., ethylene and/or isobutane) to beliberated from the absorbent and/or the absorbent to be regenerated(e.g., prepared for re-use, as disclosed herein). In an embodiment, thepressure from one or more of the reactors (e.g., reactors 1010, 1020,1030, and/or 1040) may be utilized to pressurize another of thesereactors. For example, in the embodiment of FIG. 10, the pressure of gasin reactor 1040 may be used to pressurize reactor 1020 to theintermediate pressure through line 1050, with valves 1058 and 1084 beingin an open position and valves 1082 and 1056 being in a closed position.Valves 1062, 1064, 1066, and 1068 may be switched between an openposition and a closed position to allow product nitrogen in stream 1060to flow in and out of reactors 1010, 1020, 1030, and 1040. Valves 1052,1054, 1056, and 1058 may be switched between an open position and aclosed position to allow pressurization and depressurization of reactors1010, 1020, 1030, and 1040 through stream 1050. Valves 1082, 1084, 1086,and 1088 may be switched between an open position and a closed positionto allow light gas stream 1080 to feed to reactors 1010, 1020, 1030, and1040 when in the absorption phase. Valves 1092, 1094, 1096, and 1098 maybe switched between an open position and a closed position to remove anypurge gas from reactors 1010, 1020, 1030, and 1040 through stream 1090.

In an embodiment, a stripping gas, such as isobutane or nitrogen, may beadded to the absorption reactors 1010, 1020, 1030, and 1040, forexample, through stream 1070 during the regeneration phase. Stream 1070may be positioned at a bottom of reactors 1010, 1020, 1030, and 1040 sothe stripping gas may bubble through the reactor 1010, 1020, 1030, or1040 (and through any packing materials therein). Valves 1072, 1074,1076, and 1078 may be switched between open and closed positions to addthe stripping gas to the reactors 1010, 1020, 1030, and 1040 duringregeneration. Not intending to be bound by theory, the stripping gas maylower the partial pressure of ethylene in the absorption reactors 1010,1020, 1030, and 1040 during regeneration.

In an embodiment, one or more of the absorption reactors 1010, 1020,1030, and 1040 may comprise internals to distribute the gas through theliquid absorption solvent and prevent channeling. Suitable internals mayinclude distillation packing that distributes gas and reduces axialmixing of the liquid. Internals may prevent liquid absorption solvent inthe absorption reactors 1010, 1020, 1030, and 1040 from mixing so thatsolvent flow would be first saturated and then a saturation front maymove vertically upward through the absorption reactors 1010, 1020, 1030,and 1040.

In an embodiment, separating at least one gaseous component from the gasstream comprises removing a waste stream. In an embodiment, theremaining unabsorbed gas stream components form the waste stream. In anembodiment where the absorbed component comprises ethylene and theabsorbent comprises a CuCl/aniline/DMF or a CuCl/aniline/NMP solventsystem, such a waste stream may comprise hydrogen, methane, ethane,acetylene, propylene, various other hydrocarbons, volatile contaminants,or combinations thereof. Further, such a waste stream may besubstantially free of unreacted ethylene monomers or, optionally,comonomers. As used herein, “substantially free of unreacted ethylenemonomers” means that the waste gases comprise less than 50% unreactedethylene monomers, alternatively, less than 10% unreacted ethylenemonomers, alternatively, less than 1.0% unreacted ethylene monomers,alternatively, less than 0.1 unreacted ethylene monomers, alternatively,less than 0.01% unreacted ethylene monomers by total weight of thestream.

In an embodiment, removing the waste stream may comprise cooling thewaste stream, and/or reducing or increasing the waste stream pressuresuch that the waste stream flows to the processing device 114. Forexample, in an embodiment, the waste stream may be “swept away” byconveying a suitable sweep gas (e.g., an inert or unreactive gas, asdisclosed above) through the vessel containing the waste gas (e.g., theabsorption reactor 116) at a sufficient pressure, at velocity, orcombinations thereof to expel the waste gases therefrom. For example, inthe embodiments illustrated by FIGS. 1-5, separating at least onegaseous component from the gas stream yields a waste gas stream 20 beingsubstantially free of unreacted ethylene monomers (optionally,comonomers), alternatively, a waste gas stream having a reducedconcentration of unreacted ethylene monomers (optionally, comonomers).For example, the waste gas stream may comprise less than about 30%,alternatively, less than about 25%, alternatively, less than about 20%,alternatively, less than about 15%, alternatively, less than about 10%unreacted ethylene monomers by total weight of the stream. In anadditional embodiment, the ethylene may be decreased by a percentage ofthe ethylene present in the gas stream prior to separating at least onegaseous component therefrom. For example, the waste gas stream maycomprise less than about 40%, alternatively, less than about 30%,alternatively, less than about 20% by total weight of the stream of theunreacted ethylene monomers present in the gas stream prior toseparation.

In an embodiment, separating at least one gaseous component from the gasstream may further comprise liberating the absorbed gaseous componentfrom the absorbent (e.g., in situ within absorption reactor 116 and/orin another vessel such as regenerator 120). Liberating the absorbedgaseous component from the absorbent generally comprises any suitablemeans of reversing the various links, bonds, attractions, complexes, orcombinations thereof by which the at least one gaseous component isbound, linked, bonded or combinations thereof to the absorbent or aportion thereof. Non-limiting examples of a suitable means by which toliberate the absorbed gaseous component include altering absorptionkinetics or the absorption equilibrium of the absorbent, heating ordepressurizing the absorbent, altering the partial pressure of theabsorbed gas, or combinations thereof.

In an embodiment, the absorbed gaseous component may be liberated (e.g.,desorbed and/or decomplexed) from the absorbent within the one or moreof such absorption reactors in a regeneration and/or desorption phase.In embodiments, the regeneration phase may comprise regenerating theabsorption solvent system so as to yield unreacted ethylene; inembodiments, the regeneration phase may comprise regenerating theabsorption solvent system in the absorption reactor 116 so as to yieldunreacted ethylene. For example, in the embodiment of FIGS. 1 and 2(and/or, in an embodiment where the absorption reactor 116 is configuredin a PSA configuration, as disclosed herein with respect to FIG. 10),the absorption reactor 116 may be configured to induce the release ofthe gas absorbed or complexed by the absorption solvent therefrom (e.g.,desorption and/or decomplexation of the absorbed and/or complexedethylene and/or isobutane), as disclosed in detail herein. Not intendingto be bound by theory, inducing the release of the absorbed or complexedgas may comprise altering the reaction kinetics or the gas-solventequilibrium of the absorption solvent system, the temperature of theabsorption reactor 116, the pressure of the absorption reactor 116, thepartial pressure of the absorbed gas, or combinations thereof. In suchan embodiment, the absorption reactor 116 may comprise controls, thermalconduits, electric conduits, compressors, vacuums, the like, orcombinations thereof configured to alter the reaction kinetics, thegas-solvent equilibrium, the temperature of the absorption reactor 116,the pressure of the absorption reactor 116, or combinations thereof.

For example, in an embodiment, liberating the absorbed gaseous componentmay comprise depressurizing the solution comprising the complexedethylene to a suitable partial pressure. In an additional embodiment,liberating the absorbed gaseous component may comprise heating hesolution comprising the complexed ethylene within the absorption reactor116 (alternatively, within a regenerator 120, as disclosed herein below)to a suitable temperature. Such a suitable temperature may be in a rangeof from about 110° F. to about 200° F., alternatively, from about 140°F. to about 160° F., alternatively, from about 160° F. to about 200° F.,alternatively, from about 180° F. to about 200° F., to encourage releaseof the absorbed compound (e.g., ethylene and/or isobutane) from theabsorption solvent. For example, in a particular embodiment, theabsorption reactor 116 (alternatively, the regenerator 120) may beoperated at a temperature of from about 160° F. to about 200° F.,alternatively, from about 1.80° F. to about 200° F. during theliberation of the absorbed component (e.g., ethylene and/or isobutene)from the absorption solvent. In an alternative embodiment, theabsorption reactor 116 (alternatively, the regenerator 120) may beoperated at a temperature of from about 140° F. to about 160° F. duringthe liberation of the absorbed component (e.g., ethylene and/orisobutene) from the absorption solvent. For example, such liberationtemperatures may be suitable as an economic alternative. For example,operation an absorption reactor like absorption reactor 116(alternatively, a regenerator like regenerator 120) at temperatures in arange of from about 140° F. to about 160° F. during the liberation ofthe absorbed component may require less energy, which may create a costsavings, by allowing heat derived from other sources (e.g.,polymerization reactor coolant, low pressure stream, heat-exchangersupstream of regenerators, heat-exchangers in the absorbent recycle line,polymerization reactors, flash-line heaters, flash vessels, or the like,or combinations thereof) to be utilized to heat the absorption reactorand/or the regenerator.

Additionally, in such an embodiment, the absorption reactor 116 may beconfigured to evacuate gases (e.g., a previously absorbed and thenreleased gas, such as ethylene) and/or to facilitate the release of theabsorbed gas via a pressure differential. The absorption reactor 116 maybe configured to provide or maintain a suitable partial pressure. Such asuitable partial pressure may be in a range of from about 0.1 psig toabout 40 psig, alternatively, from about 5 psig to about 30 psig,alternatively, from about 5 psig to about 15 psig. In an embodiment, theabsorption reactor 116 may be configured to provide or maintain anethylene partial pressure in a range of from about 0 psia to about 5psia.

In an alternative embodiment, separating at least one gaseous componentfrom the gas stream may further comprise removing the solutioncomprising the absorbed component complex (e.g., the absorbed ethylenecomplex) for further processing. In such an alternative embodiment, theabsorption complex comprising the absorbed gaseous component may beremoved from the absorption reactor 116 to the regenerator 120 forliberation of the absorbed gaseous component and/or regeneration of theabsorption complex as a complexed stream 28. In embodiments, theregenerator 120 may regenerate the absorption solvent system so as toyield unreacted ethylene; in embodiments, the regenerator 120 mayregenerate the absorption solvent system in the regenerator 120 so as toyield unreacted ethylene.

In such an embodiment, the complexed stream 28 may comprise ethylene,ethane, and/or isobutane. Ethylene may be present in a range of fromabout 0.1% to about 10%, alternatively, from about 0.4% to about 5%,alternatively, from about 0.5% to about 2.5% by total weight of thestream. Ethane may be present in a range of from about 0.1% to about 1%,alternatively, from about 0.2% to about 0.5% by total weight of thestream. Isobutane may be present in a range of from about 0.1% to about1%, alternatively, from about 0.2% to about 0.5% by total weight of thestream.

In one or more of the embodiments disclosed herein, separating acomplexed stream into a recycle stream and an absorbent stream (e.g., atblock 92) comprises liberating the absorbed gaseous component from theabsorbent. As explained above, liberating the absorbed gaseous componentfrom the absorbent generally comprises any suitable means for reversingthe various links, bonds, attractions, complexes, or combinationsthereof by which the at least one gaseous component is bound, linked,bonded or combinations thereof to the absorbent or a portion thereof.Various processes and/or parameters for liberating an absorbed gaseouscomponent were disclosed above with respect to liberation within theabsorption reactor.

In the embodiment illustrated by FIG. 5, separating a complexed streaminto a recycle stream and an absorbent stream may comprise routing thecomplexed stream 28 to the regenerator 120. In one or more one or moreof the embodiments disclosed herein, a regenerator 120 may comprise adevice or apparatus configured to recover, regenerate, recycle, and/orpurify an absorption solvent and/or to liberate an absorbed gas.Non-limiting examples of a suitable regenerator include a flash reactor,a depressurization reactor, a solvent regeneration reactor, orcombinations thereof.

In an embodiment, regenerator 120 may be configured to operate on thebasis of a pressure differential. In such an embodiment, the regenerator120 may be configured to provide or maintain a suitable internalpressure. Such a suitable internal pressure may be in a range of fromabout 0 psig to about 150 psig, alternatively, from about 5 psig toabout 30 psig, alternatively, from about 5 psig to about 15 psig,alternatively, from about 0 psig to about 10 psig. In an embodiment, theregenerator 120 may be configured to provide or maintain a suitablepartial pressure. Such a suitable partial pressure may be in a range offrom about 0 psia to about 50 psia.

In an embodiment, regenerator 120 may be configured to operate on thebasis of an elevated temperature. Such a regenerator 120 may beconfigured to provide or maintain a suitable temperature. Such asuitable temperature may be in a range of from about 110° F. to about200° F., alternatively, from about 140° F. to about 200° F.,alternatively, from about 140° F. to about 160° F., alternatively, fromabout 160° F. to about 200° F., alternatively, from about 180° to about200° F., to vaporize and/or release an absorbed compound (e.g., ethyleneand/or isobutane) from the absorption solvent. In an embodiment,regenerator 120 (e.g., like the absorption reactor 116) may be heated todesorb, or regenerate, the absorption solvent system using heat sourcescomprising cooling water, low-pressure steam, or combinations thereof.Cooling water, low pressure steam, or a combination thereof may besuitable for heating regenerator 120 (or the absorption reactor 116, asdisclosed above) to a temperature of from about 140° F. to about 200° F.

In an embodiment, the regenerator 120 may be configured for batch and/orcontinuous processes. For example, in an embodiment, a PEP system maycomprise two or more absorption regenerators (e.g., such as regenerators1220 and 1222 of FIG. 12), each of which may be configured for batchoperation. As explained above, by employing two or more absorptionreactors, such a system may operate to regenerate the absorbentcontinuously.

In an embodiment, separating a complexed stream into a recycle streamand an absorbent stream may yield a regenerated absorbent stream whichmay be reused in an absorption reaction and a recycle stream comprisingunreacted monomers (optionally, comonomers) which may be reintroducedinto or reused in a PEP process. For example, in the embodimentillustrated by FIG. 5, separating a complexed stream 28 into a recyclestream and an absorbent stream yields a recycle stream 22 which may bereturned to the purifier 102, for example, and a regenerated absorbentstream 30 which may be returned to the absorption reactor 116, forexample.

In an embodiment, liberating the absorbed gas may also yield a recyclestream comprising unreacted monomers (optionally, comonomers) which maybe returned to the separator 108 for pressurization (e.g., via one ormore compressors located at the separator 108). For example, in theembodiments illustrated by FIGS. 1-5, liberating the absorbed gas yieldsa recycle stream 22 which may be returned to the separator 108, 105.Pressurizing the recycle stream 22 may yield a reintroduction stream(not shown) which may be reintroduced into or reused in a PEP process.For example, in the embodiments illustrated by FIGS. 1-5, areintroduction stream may be introduced into the purifier 102. In analternative embodiment, a recycle stream (such as recycle stream 22) maybe pressurized and/or reintroduced into a PEP process without beingreturned to the separator 108, 105. In an embodiment, the recycle stream22 may comprise substantially pure ethylene; alternatively, the recyclestream 22 may comprise ethylene and butane, particularly, isobutane. Inan embodiment, the gas stream may comprise may comprise nitrogen,ethylene, ethane, and/or isobutane. Ethylene may be present in a rangeof from about 65% to about 99%, alternatively, from about 70% to about90%, alternatively, about 75% to about 85% by total weight of thestream. Ethane may be present in a range of from about 1% to about 20%,alternatively, from about 5% to about 15%, alternatively, from about7.5% to about 12.5% by total weight of the stream. Isobutane may bepresent in a range of from about 1% to about 20%, alternatively, fromabout 5% to about 15%, alternatively, from about 7.5% to about 12.5% bytotal weight of the stream.

In one or more one or more of the embodiments disclosed herein,combusting waste gas stream (e.g., at block 66 or 76) may generallycomprise burning or incinerating one or more gaseous components of thewaste gas stream 20. In an embodiment, combusting the waste gas stream20 may further or alternatively comprise cracking, catalytic cracking,pyrolysis, dehydrogenation, scrubbing, converting, treating, orcombinations thereof, of the waste gas stream 20 or combustion products.

As disclosed herein, the waste gas stream 20 may comprise volatilizedsolvents, unreacted gases, secondary products, contaminants,hydrocarbons, or combinations thereof. In an embodiment, the waste gasstream 20 may comprise hydrogen, nitrogen, methane, ethylene, ethane,propylene, propane, butane, isobutane, heavier hydrocarbons, orcombinations thereof. Ethylene may be present in a range of from about1% to about 40%, alternatively, from about 2.5% to about 20% by totalweight of the stream. Ethane may be present in a range of from about 5%to about 50%, alternatively, from about 30% to about 40% by total weightof the stream. Isobutane may be present in a range from about 1% toabout 20%, alternatively, from about 1.5% to about 5%, alternatively,from about 2% to about 3% by total weight of the stream. Nitrogen may bepresent in a range from about 10% to about 80%, alternatively, fromabout 35% to about 50%, alternatively, from about 40% to about 45% bytotal weight of the stream.

In embodiments as illustrated by FIGS. 1-5, combusting waste gas streammay comprise routing the waste gas stream 20 to the processing device114. In one or more of the embodiments disclosed herein, the processingdevice 114 may comprise a combustion device or apparatus, such as aflare. Non-limiting examples of a suitable flare include a torch,incinerator, the like, or combinations thereof. A flare may suitablycomprise one or more controllable nozzles, an ignition source, a bypassvalve, a pressure relief valve, or combinations thereof. The flare maybe configured to provide an environment for the combustion of variouswaste products, for example, atomic gases (e.g. nitrogen, oxygen),oxides (e.g. carbon monoxide, oxides of nitrogen or sulfur), variousunwanted gaseous products, or combinations thereof. In an embodiment,the flare may additionally comprise a device or apparatus configured toselectively remove one or more of contaminants prior to, during, and/orafter combustion (e.g., such that a given combustion product is notreleased into the atmosphere).

In one or more of the embodiments disclosed herein, the processingdevice 114 may comprise a cracker, catalytic cracker, scrubber,converter, treater, dehydrogenator, deoxygenator, or combinationsthereof, for example. In an embodiment, processing device 114 maycomprise an ethylene cracker. In the processing device 114, one or moregaseous components, such as ethane, from waste gas stream 20 may beconverted to a desired product, such as ethylene monomer. The desiredproduct formed in the processing device 114 may be recycled to one ormore of purifier 102, reactor 104, reactor 106, for example.

In other alternative embodiments, waste gas stream 20 may be used asfuel (for example for steam generation or co-gen operations, and/or maybe used as fuel and/or a feed to a thermal cracking unit to formethylene (e.g., to form feed stream 10). In another alternativeembodiment, the waste gas from waste gas stream 20 may be exported fromthe plant to a monomer plant.

In an embodiment, implementation of one or more of the disclosed systems(e.g., PEP systems 100, 200, 300, 400, and/or 500) and/or processes(e.g., PEP processes 600, 700, 800 and/or 900) may allow for therecovery of a substantial portion of the ethylene monomers that wouldotherwise be lost due to the operation of such systems or processes, forexample, by flaring. In an embodiment, one or more of the disclosedsystems may allow for the recovery of up to about 75%, alternatively, upto about 85%, alternatively, up to about 90%, alternatively, up to about95% by total weight of the stream of the ethylene monomers that wouldotherwise be lost. In an embodiment, one or more of the disclosedsystems may allow for the recovery of up to about 75%, alternatively, upto about 85%, alternatively, up to about 90%, alternatively, up to about95% by total weight of the stream of the isobutane that would otherwisebe lost. The recovery of such a portion of the unreacted ethylenemonomers may yield a significant economic benefit, for example, byimproving the efficiency of usage of ethylene monomers and decreasingcapital inputs associated with the acquisition of ethylene monomers.Similarly, the recovery of such a portion of isobutane may yield asignificant economic benefit, for example, by decreasing capital inputsassociated with the acquisition of isobutane and/or by reducing thepresence of isobutane in flare emissions.

In an embodiment, implementation of one or more of the disclosed systemsand/or processes may decrease the amount of ethane and/or hydrogen thatis transferred to polymerization reactor 106. In an embodiment,implementation of one or more of the disclosed systems and/or processesmay decrease the amount of ethane and/or hydrogen that is returned to apolymerization reactor (such as reactors 104 and/or 106) via a recyclestream. By decreasing the amount of ethane contained in a stream to apolymerization reactor, the overall efficiency of the polyethyleneproduction may be improved (for example, by increasing the ethyleneconcentration without reaching the bubble point in the loop reactor).For example, decreasing the amount of ethane in a stream may improvepolymerization reactor efficiency, improve catalyst efficiency, reducepolymer fouling, reduce polymerization downtime, improve production ofbimodal polymer types, improve production of copolymers, or combinationsthereof.

The various embodiments shown in the Figures may be simplified and maynot illustrate common equipment such as heat exchangers, pumps, andcompressors; however, a skilled artisan would recognize the disclosedprocesses and systems may include such equipment commonly usedthroughout polymer manufacturing.

A skilled artisan will recognize that industrial and commercialpolyethylene manufacturing processes may necessitate one or more, oftenseveral, compressors or similar apparatuses. Such compressors are usedthroughout polyethylene manufacturing, for example to pressurizereactors 104, 106 during polymerization. Further, a skilled artisan willrecognize that a polyethylene manufacturing process includes one or moredeoxygenators and/or similar de-oxidizing apparatuses, for instancepurifying solvents or reactants and/or for purging reactors of oxygen.Because the infrastructure and the support therefore, for example toprovide power and maintain the compressors and/or deoxygenators, alreadyexists within a commercial polyethylene manufacturing plant,reallocating a portion of these available resources for use in thedisclosed systems may necessitate little, if any, additional capitalexpenditure in order to incorporate the disclosed systems and orprocesses.

Further, because compressors, deoxygenators, and various othercomponents are already employed in various polyethylene processes andsystems, the opportunity for increased operation of such apparatuses mayimprove the overall efficiency of polyethylene production systems andprocesses. For example, when a portion of a PEP process or system istaken off-line for maintenance and/or repair, other portions of thesystem (e.g., a compressor, a deoxygenator, a reactor, etc.) maycontinue to provide service according to the current processes.Operating and/or reallocating resources for operation of the disclosedPEP systems and/or processes may thereby increase the efficiency withwhich conventional systems are used.

Additional Description

Processes and systems for the component separation in a polymerizationsystem have been described. The following clauses are offered as furtherdescription:

Embodiment A

A process for component separation in a polymer production system,comprising:

separating a polymerization product stream into a gas stream and apolymer stream, wherein the gas stream comprises ethane and unreactedethylene;

distilling the gas stream into a light hydrocarbon stream, wherein thelight hydrocarbon stream comprises ethane and unreacted ethylene;

contacting the light hydrocarbon stream with an absorption solventsystem, wherein at least a portion of the unreacted ethylene from thelight hydrocarbon stream is absorbed by the absorption solvent system;and

recovering a waste gas stream from the absorption solvent system,wherein the waste gas stream comprises ethane, hydrogen, or combinationsthereof.

Embodiment B

The process of embodiment A, further comprising:

regenerating the absorption solvent system to yield recovered ethylene.

Embodiment C

The process of embodiment A through B, further comprising:

distilling the gas stream into a side stream comprising isobutane.

Embodiment D

A process for component separation in a polymer production system;comprising:

separating a polymerization product stream into a gas stream and apolymer stream, wherein the gas stream comprises ethane and unreactedethylene;

distilling the gas stream into an intermediate hydrocarbon stream and afirst bottoms stream, wherein the intermediate hydrocarbon streamcomprises ethane, ethylene, and isobutane;

distilling the intermediate hydrocarbon stream into a light hydrocarbonstream and a second bottoms stream, wherein the light hydrocarbon streamcomprises ethane and ethylene;

contacting the light hydrocarbon stream with an absorption solventsystem, wherein at least a portion of the unreacted ethylene from thelight hydrocarbon stream is absorbed by the absorption solvent system;and

recovering a waste gas stream from the absorption solvent system,wherein the waste gas stream comprises ethane, hydrogen, or combinationsthereof.

Embodiment E

The process of embodiment D, further comprising:

regenerating the absorption solvent system to yield recovered ethylene.

Embodiment F

The process of embodiment D through E, further comprising:

distilling the intermediate hydrocarbon stream into a side streamcomprising isobutane, wherein the second bottoms stream comprisesisobutane, wherein the second bottoms stream is substantially free ofolefins.

Embodiment G

A process for component separation in a polymer production system,comprising:

polymerizing olefin monomers in a first polymerization reactor to yielda mid-polymerization product stream;

separating the mid-polymerization product stream into a mid-gas streamand a mid-polymer stream, wherein the mid-gas stream comprises ethane,unreacted ethylene, and hydrogen; and

polymerizing the mid-polymer stream in a second polymerization reactor.

Embodiment H

The process of embodiment G, the step of separating comprising reducinga pressure of the mid-polymerization product stream so as to flashethylene, ethane; hydrogen, or combinations thereof.

Embodiment I

A process for component separation in a polymer production system,comprising:

polymerizing olefin monomers in a first polymerization reactor;

separating a mid-polymerization product stream into a mid-gas stream anda mid-polymer stream, wherein the mid-gas stream comprises ethane andunreacted ethylene;

polymerizing the mid-polymer stream in a second polymerization reactor;and

introducing a scavenger prior to the second polymerization reactor.

Embodiment J

The process of embodiment I, the introducing a scavenger prior to thesecond polymerization reactor comprising introducing the scavenger intothe mid-polymerization product stream.

Embodiment K

The process of embodiment I through wherein the scavenger comprises ahydrogenation catalyst.

Embodiment L

The process of embodiment I through K, wherein the step of separatingcomprises:

reducing a pressure of the mid-polymerization product stream so as toflash ethylene and ethane.

Embodiment M

The process of embodiment I through L, wherein the scavenger reduces aconcentration of hydrogen prior to the second polymerization reactor.

Embodiment N

A process for component separation in a polymer production system,comprising:

polymerizing olefin monomers in a first polymerization reactor to yielda mid-polymerization product stream;

degassing at least a portion of hydrogen from the mid-polymerizationproduct stream to yield a hydrogen-reduced product stream;

separating the hydrogen-reduced product stream into a mid-gas stream anda mid-polymer stream, wherein the mid-gas stream comprises ethane andunreacted ethylene; and

polymerizing the mid-polymer stream in a second polymerization reactor.

Embodiment O

The process of embodiment N the step of separating comprising reducing apressure of the hydrogen-reduced product stream so as to flash ethyleneand ethane.

Embodiment P

The process of embodiment N through O, wherein an amount of hydrogen inthe mid-gas stream comprises less than about 1 wt %.

Embodiment Q

The process of embodiments G through N, further comprising:

contacting the mid-gas stream with an absorption solvent system, whereinat least a portion of the unreacted ethylene from the mid-gas stream isabsorbed by the absorption solvent system; and

regenerating the absorption solvent system to yield recovered ethylene.

Embodiment R

The process of embodiment Q, further comprising:

recovering a waste gas stream from the absorption solvent system,wherein the waste gas stream comprises ethane.

Embodiment S

The process of embodiments A through F or R, further comprising:

processing the waste gas stream in a processing device.

Embodiment T

The process of embodiment S, wherein the processing device comprises acracker, catalytic cracker, scrubber, converter, treater,dehydrogenator, deoxygenator, flare or combinations thereof.

Embodiment U

The process of embodiments A through F or Q through T, wherein theabsorbent solvent system is configured to operate at a temperature in arange of from about 40° F. to about 110° F.

Embodiment V

The process of embodiments A through F or Q through U, wherein theabsorbent solvent system comprises copper chloride, aniline, andN-methylpyrrolidone.

EXAMPLES

The disclosure having been generally described, the following examplesare given as particular embodiments of the disclosure and to demonstratethe practice and advantages thereof. It is understood that theseexamples are given by way of illustration and is not intended to limitthe specification or the claims in any manner.

A computerized commercial process simulator was employed to generate anoutput from a model in accordance with the systems and/or processesdisclosed herein. The model employed is illustrated at FIG. 12, whichshows an embodiment of an absorption system 1200, as disclosed herein,and shall be used to describe the examples below. In the embodimentshown in FIG. 12, a light gas stream 1218, which was separated from apolymerization product stream of a polyethylene reactor 104, 106disclosed in an embodiment of PEP systems 100, 200, 300, 400, or 500 ofFIGS. 1 to 5, feeds to an absorption reactor 1216. The total molar andmass flows and component molar and mass flows of the light gas stream1218 are shown in Table 1 below:

TABLE 1 Total Molar Flow 52.9 Total Mass Flow 1127 (lbmol/hr) (lb/hr)Component Molar Flow Component Mass Flow (lbmol/hr) (lb/hr) Hydrogen15.4 Hydrogen 31 Nitrogen 4.9 Nitrogen 137 Ethylene 26 Ethylene 729Ethane 5.6 Ethane 169 Isobutane 1.1 Isobutane 62 Component MolarComponent Mass Fraction Fraction Hydrogen 0.291 Hydrogen 0.028 Nitrogen0.092 Nitrogen 0.121 Ethylene 0.491 Ethylene 0.646 Ethane 0.106 Ethane0.150 Isobutane 0.020 Isobutane 0.055

Unreacted ethylene that enters the absorption reactor 1216 is absorbedin the absorption solvent system within the absorption reactor 1216.Absorbed unreacted ethylene flows, as complexed stream 1228, to a firstregenerator 1220. In stream 1228, the absorbed ethylene is heated byheat exchanger REG1HEAT before entering the first regenerator 1220.Ethylene desorbs from the solvent from the absorption solvent system infirst regenerator 1220 and flows through stream 1229 to a secondregenerator 1222. Stream 1229 may be cooled with heat exchanger REG2COOLbefore entering the second regenerator 1222. Ethylene is recovered instream 1224. Absorption solvent in streams 1232 and 2134 combine in heatexchanger FEEDCOOL to recycle to the absorption reactor 1216 in stream1230.

Table 2 shows operating conditions for examples 1-44 of ethylenerecovery using the system 1200 of FIG. 12. For the examples shown inTable 2, the absorption solvent system comprises a copper chloride,aniline, and NMP system, as disclosed herein, and composition of thepurified product is based on 90% ethylene recovery. The composition ofthe purified product recovered from stream 1224 in FIG. 12 comprisesethylene, ethane, nitrogen, hydrogen, and isobutane. The wt % of each ofthese components in the purified product is shown in Table 2. Selectexamples from Table 2 are discussed in detail below.

Example 3

In Example 3 of Table 2, the absorption reactor 1216 in FIG. 12 operatesat a temperature of 15° F., with a lean solvent temperature of 14° F.and pressure of 40 psig. The first regenerator 120 operates at atemperature of 150° F. and pressure of 0 psig. The second regenerator122 operates at a temperature of 50° F. and pressure of 0 psig. Underthese conditions, system 900 recovers 90% of the ethylene and thesolvent circulation flow rate to 344,776 lb/hr and the amount ofethylene in the purified product to 64.5%.

Example 4

In Example 4 of Table 2, the operating conditions are the same asExample 3, except the first regenerator 1220 operates at a temperatureof 200° F. and pressure of 0 psig. Under these conditions, system 900recovers 90% of ethylene for a solvent circulation flow rate of 143,736lb/hr, and the purified product contains 77.5% ethylene.

Example 7

In Example 7 of Table 2, the absorption reactor 1216 in FIG. 12 operatesat a temperature of 53° F., with a lean solvent temperature of 50° F.Absorption reactor 1216 also operates at a pressure of 40 psig. Thefirst regenerator 120 operates at a temperature of 150° F. and apressure of 0 psig. The second regenerator 1222 operates at atemperature of 50° F. and a pressure of 0 psig. Under these conditions,system 900 recovers 90% of the ethylene for a solvent circulation flowrate of 53,920 lb/hr. The purified product composition for Example 7 isshown in Table 2.

When comparing Example 7 with the Examples 3 and 4, the solventcirculation flow rate of 53,920 lb/hr in Example 7 is less than the flowrates of 143,736 lb/hr and 344,776 lb/hr in the Examples 3 and 4. Thus,Example 7 shows the solvent circulation flow rate required to absorbethylene in a copper chloride aniline NMP absorption solvent system ismuch less for an absorption temperature of 53° F. than for an absorptiontemperature of 15° F. because of the unexpected drop in solubility forethylene in the absorption solvent system for temperatures below about50° F.

Example 8

In Example 8 of Table 2, the absorption reactor 1216 in FIG. 12 operatesat a temperature of 55° F., with a lean solvent temperature of 50° F.Absorption reactor 1216 also operates at a pressure of 40 psig. Thefirst regenerator 1220 operates at a temperature of 200° F. and apressure of 0 psig. The second regenerator 1222 operates at atemperature of 50° F. and a pressure of 0 psig. Under these conditions,system 800 recovers 90% of the ethylene for a solvent circulation flowrate of 47,785 lb/hr. The purified product composition for Example 8 isshown in Table 2.

Example 8 confirms the results shown in Example 7 that lower solventcirculation flow rates are required when the absorption reactor 1216operates at a temperature of 55° F. instead of temperatures below 50° F.Example 2 additionally shows varying the temperature of the regenerator1220 from 150° F. to 200° F. does not affect the solvent circulationflow rate to a significant degree.

Example 19

In Example 19 of Table 2, the absorption reactor 1216 in FIG. 12operates at a temperature of 53° F., with a lean solvent temperature of50° F. Absorption reactor 1216 also operates at a pressure of 40 psig.The first regenerator 1220 operates at a temperature of 200° F. and apressure of 10 psig. The second regenerator 1222 operates at atemperature of 50° F. and a pressure of 10 psig. Under these conditions,system 1200 recovers 90% of the ethylene for a solvent circulation flowrate of 59,272 lb/hr. The purified product composition is shown in Table2.

Example 19 confirms the lower solvent circulation rates discussed inExamples 7 and 8 when compared to Examples 3 and 4. Example 19 alsoshows varying the pressure of the first and second regenerators 1220 and1222 between 0 psig and 10 psig does not significantly alter results.Operation of the regenerators 1220 and 1222 at 0 psig may provide alower solvent circulation rate as well as enhanced product purity, andoperation of the regenerators 1220 and 1222 at 10 psig may provide asafer design because a positive pressure in the regenerators 1220 and1222 reduces a chance of air and water infiltration via leaks in thesystem and process, which may react with copper chloride in theabsorption solvent system and inhibit performance.

Example 28

In Example 28 of Table 2, the absorption reactor 1216 in FIG. 12operates at 52° F., with a lean solvent temperature of 50° F. Absorptionreactor 1216 also operates at a pressure of 60 psig. The firstregenerator 1220 operates at a temperature of 100° F. and a pressure of0 psig. The second regenerator 1222 operates at a temperature of 50° F.and a pressure of 0 psig. Under these conditions, system 1200 recovers90% of the ethylene for a solvent circulation flow rate of 58,613 lb/hr.The purified product composition is shown in Table 2.

Under the conditions in Example 28, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 29

In Example 29 of Table 2, the absorption reactor 1216 in FIG. 12operates at 55° F., with a lean solvent temperature of 50° F. Absorptionreactor 1216 also operates at a pressure of 60 psig. The firstregenerator 1220 operates at a temperature of 150° F. and a pressure of0 psig. The second regenerator 1222 operates at a temperature of 50° F.and a pressure of 0 psig. Under these conditions, system 1200 recovers90% of the ethylene for a circulation flow rate of solvent of 51,106lb/hr. The purified product composition is shown in Table 2.

Under the conditions in Example 29, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 30

In Example 30 of Table 2, the absorption reactor 1216 in FIG. 12operates at 56° F., with a lean solvent temperature of 50° F. Absorptionreactor 1216 also operates at a pressure of 60 psig. The firstregenerator 1220 operates at a temperature of 200° F. and a pressure of0 psig. The second regenerator 1222 operates at a temperature of 50° F.and a pressure of 0 psig. Under these conditions, system 1200 recovers90% of the ethylene for a circulation flow rate of solvent of 46,744lb/hr. The purified product composition is shown in Table 2.

Under the conditions in Example 30, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 33

In Example 33 of Table 2, the absorption reactor 1216 in FIG. 12operates at a temperature of 102° F., with a lean solvent temperature of100° F. Absorption reactor 1216 also operates at a pressure of 60 psig.The first regenerator 1220 operates at a temperature of 200° F. and apressure of 0 psig. The second regenerator 1222 operates at atemperature of 50° F. and a pressure of 0 psig. Under these conditions,system 900 recovers 90% of the ethylene for a solvent circulation flowrate of 63,435 lb/hr. The purified product composition for Example 33 isshown in Table 2.

Under the conditions in Example 33, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher. Moreover, Example 33 showthat operation of the absorption reactor 116 at temperatures higher thanthe temperatures of maximum solubility shown in the solubility graph,for example, at 102° F. as shown in Example 33, may still proveeconomically feasible because, for example, solvent circulation flowrates remain low compared with conditions of Examples 3 and 4.

Example 40

In Example 40 of Table 2, the absorption reactor 1216 in FIG. 12operates at a temperature of 52° F., with a lean solvent temperature of50° Absorption reactor 1216 also operates at a pressure of 60 psig. Thefirst regenerator 1220 operates at a temperature of 150° F. and apressure of 10 psig. The second regenerator 1222 operates at atemperature of 50° F. and a pressure of 10 psig. Under these conditions,system 1200 recovers 90% of the ethylene for a solvent circulation flowrate of 57,441 lb/hr. The purified product composition for Example 40 isshown in Table 2.

Under the conditions in Example 40, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example 41

In Example 41 of Table 2, the absorption reactor 1216 in FIG. 12operates at 55° F., with a lean solvent temperature of 50° F. Absorptionreactor 1216 also operates at a pressure of 60 psig. The firstregenerator 1220 operates at a temperature of 200° F. and a pressure of10 psig. The second regenerator 1222 operates at a temperature of 50° F.and a pressure of 10 psig. Under these conditions, system 900 recovers90% of the ethylene for a circulation flow rate of solvent of 51,482lb/hr. The purified product composition is shown in Table 2.

Under the conditions in Example 41, the solvent circulation flow rate isless than that of the Examples 3 and 4, and the amount of ethylene inthe purified product is significantly higher.

Example Simulation

A computerized commercial process simulator was employed to generate anoutput from another model in accordance with the systems and/orprocesses disclosed herein. The model employed is illustrated at FIG.13, wherein a gaseous stream, designated VAP FEED (e.g., the light gasstream disclosed herein) feeds to absorption reactor ASORB1. The outputgenerated by the commercial process simulator is a material balance anda heat balance, shown in Table 3. The names designating the variousstreams listed in Table 3 correspond to streams illustrated in FIG. 10.In FIG. 13, ASORB1 is the absorption reactor, which is shown as a fourstage absorber operating at 90° F.

TABLE 2 Lean Absorber REG1 REG2 Absorber REG1 REG2 Flow rate of Solventtop temperature temperature temperature pressure temperature temperatureEthylene circulation solvent Ethylene Ethane Nitrogen Hydrogen IsobutaneExample Temp. (° F.) (° F.) (° F.) (° F.) (psig) (psig) (psig) Recovery(lb/hr) (wt %) (wt %) (wt %) (wt %) (wt %) 1 14 15 50 50 40 0 0 90%1704044 48.9% 11.6% 10.0% 27.2% 2.2% 2 14 15 100 50 40 0 0 90% 73133757.7% 13.0% 11.1% 18.9% 2.3% 3 14 15 150 50 40 0 0 90% 344776 64.5%15.2% 8.5% 9.5% 2.2% 4 14 15 200 50 40 0 0 90% 143736 77.5% 16.3% 2.1%3.3% 0.8% 5 50 50 50 50 40 0 0 90% 672565 62.1% 13.3% 7.0% 15.1% 2.5% 650 51 100 50 40 0 0 90% 158735 81.9% 11.2% 1.8% 4.1% 1.0% 7 50 53 150 5040 0 0 90% 53920 95.9% 2.3% 0.5% 1.1% 0.3% 8 50 55 200 50 40 0 0 90%47785 96.5% 1.9% 0.4% 1.0% 0.3% 9 100 100 100 50 40 0 0 90% 921807 62.1%13.0% 7.1% 15.3% 2.5% 10 100 100 150 50 40 0 0 90% 343211 78.4% 9.5%3.2% 7.1% 1.9% 11 100 101 200 50 40 0 0 90% 88403 95.6% 1.9% 0.7% 1.4%0.4% 12 14 14 50 50 40 10 10 N/A 13 14 15 100 50 40 10 10 90% 132171950.3% 12.0% 10.2% 25.3% 2.2% 14 14 14 150 50 40 10 10 90% 685442 56.2%13.3% 10.6% 17.7% 2.3% 15 14 15 200 50 40 10 10 90% 420362 64.1% 14.8%7.1% 11.7% 2.4% 16 50 50 50 50 40 10 10 90% 1367657 54.8% 11.8% 9.0%22.2% 2.2% 17 50 50 100 50 40 10 10 90% 463945 66.9% 14.6% 5.1% 11.1%2.3% 18 50 51 150 50 40 10 10 90% 121635 86.6% 8.1% 1.3% 3.1% 0.8% 19 5053 200 50 40 10 10 90% 59272 95.6% 2.5% 0.5% 1.2% 0.3% 20 100 100 100 5040 10 10 90% 1828349 54.8% 11.6% 9.0% 22.3% 2.2% 21 100 100 150 50 40 1010 90% 880270 64.5% 12.7% 5.7% 14.7% 2.4% 22 100 100 200 50 40 10 10 90%415884 77.5% 9.6% 2.3% 8.4% 2.1% 23 14 15 50 50 60 0 0 90% 858069 50.7%12.0% 10.4% 24.7% 2.2% 24 14 15 100 50 60 0 0 90% 384021 58.5% 13.9%11.4% 13.7% 2.5% 25 14 15 150 50 60 0 0 90% 159379 71.6% 16.9% 4.5% 5.6%1.4% 26 14 16 200 50 60 0 0 90% 93956 82.2% 12.7% 1.7% 2.8% 0.7% 27 5050 50 50 60 0 0 90% 296859 68.5% 14.6% 4.6% 9.8% 2.5% 28 50 52 100 50 600 0 90% 58613 93.9% 3.4% 0.7% 1.6% 0.4% 29 50 55 150 50 60 0 0 90% 5110694.7% 2.9% 0.6% 1.4% 0.4% 30 50 56 200 50 60 0 0 90% 46744 95.3% 2.6%0.5% 1.3% 0.3% 31 100 100 100 50 60 0 0 90% 428830 68.5% 13.3% 5.0%10.6% 2.6% 32 100 100 150 50 60 0 0 90% 111161 90.5% 4.1% 1.5% 3.0% 0.9%33 100 102 200 50 60 0 0 90% 63435 95.7% 1.8% 0.7% 1.4% 0.4% 34 14 14 5050 60 10 10 N/A 35 14 15 100 50 60 10 10 90% 693610 52.5% 12.5% 10.6%22.1% 2.3% 36 14 15 150 50 60 10 10 90% 346101 60.5% 14.3% 10.5% 12.3%2.4% 37 14 15 200 50 60 10 10 90% 181196 71.0% 16.3% 4.4% 6.7% 1.6% 3850 50 50 50 60 10 10 90% 669442 58.7% 12.6% 8.2% 18.2% 2.3% 39 50 51 10050 60 10 10 90% 179196 75.0% 15.2% 2.6% 5.8% 1.4% 40 50 52 150 50 60 1010 90% 57441 94.1% 3.3% 0.7% 1.6% 0.4% 41 50 55 200 50 60 10 10 90%51482 94.8% 2.9% 0.5% 1.4% 0.4% 42 100 100 100 50 60 10 10 90% 89670758.7% 12.4% 8.3% 18.3% 2.1% 43 100 100 150 50 60 10 10 90% 378813 71.8%12.1% 4.1% 9.6% 2.4% 44 100 100 200 50 60 10 10 90% 130215 89.1% 4.8%14.3% 3.7% 1.1%

TABLE 3 Substream: MIXED L1CUCLL L2CUCLR L3CUCLR2 L4CUCLR3 L5CUCLLL6CUCLL LKO1 LKO2 LKO3 V1 Mole Flow lbmol/hr C2 = 1.949416 41.8580141.85801 41.85801 1.949413 1.949413 2.02E−04 4.41E−03 9.89E−04 3.172776C2 0.9764562 5.916248 5.916248 5.916248 0.9764532 0.9764532 6.17E−048.14E−04 2.10E−04 5.654325 N2 1.15E−03 0.1711679 0.1711679 0.17116791.15E−03 1.15E−03 8.35E−06 8.99E−07 6.78E−08 7.187729 IC4 0.86150883.112527 3.112527 3.112527 0.8615092 0.8615092 2.14E−04 2.23E−031.08E−03 0.1670439 CUCL 131.4402 131.4402 131.4402 131.4402 131.4402131.4402 1.50E−13 2.85E−13 0 1.50E−13 ANILINE 580.5749 580.5749 580.5749580.5749 580.5748 580.5748 2.47E−03 0.2059512 0.0219362 2.48E−03 NMP789.7864 789.7864 789.7864 789.7864 789.7864 789.7864 2.38E−03 0.19611999.42E−03 2.38E−03 Mole Frac C2 = 1.29E−03 0.0269554 0.0269554 0.02695541.29E−03 1.29E−03 0.0343637 0.0107758 0.0294004 0.1960108 C2 6.49E−043.81E−03 3.81E−03 3.81E−03 6.49E−04 6.49E−04 0.1047838 1.99E−03 6.25E−030.3493185 N2 7.64E−07 1.10E−04 1.10E−04 1.10E−04 7.64E−07 7.64E−071.42E−03 2.19E−06 2.02E−06 0.4440506 IC4 5.72E−04 2.00E−03 2.00E−032.00E−03 5.72E−04 5.72E−04 0.0362971 5.44E−03 0.032152 0.0103198 CUCL0.0873014 0.0846439 0.0846439 0.0846439 0.0873014 0.0873014 2.54E−116.97E−13 0 9.24E−15 ANILINE 0.3856129 0.3738747 0.3738747 0.37387470.3856128 0.3856128 0.4198489 0.5029009 0.6521121 1.53E−04 NMP 0.52456940.5086013 0.5086013 0.5086013 0.5245694 0.5245694 0.4032882 0.47889450.2800845 1.47E−04 Mass Flow lb/hr C2 = 54.68846 1174.274 1174.2741174.274 54.68837 54.68837 5.68E−03 0.1238009 0.027745 89.00829 C229.36169 177.8994 177.8994 177.8994 29.3616 29.3616 0.0185606 0.02447756.32E−03 170.0235 N2 0.0322059 4.795009 4.795009 4.795009 0.03220580.0322058 2.34E−04 2.52E−05 1.90E−06 201.3533 IC4 50.07382 180.9106180.9106 180.9106 50.07384 50.07384 0.0124277 0.129461 0.06286369.709158 CUCL 13012.41 13012.41 13012.41 13012.41 13012.41 13012.411.48E−11 2.83E−11 0 1.48E−11 ANILINE 54067.97 54067.97 54067.97 54067.9754067.96 54067.96 0.2303272 19.17989 2.042886 0.2311832 NMP 78293.5878293.58 78293.58 78293.58 78293.58 78293.58 0.2355062 19.441870.9339974 0.2358215 Mass Frac C2 = 3.76E−04 7.99E−03 7.99E−03 7.99E−033.76E−04 3.76E−04 0.0112959 3.18E−03 9.03E−03 0.1891534 C2 2.02E−041.21E−03 1.21E−03 1.21E−03 2.02E−04 2.02E−04 0.0369193 6.29E−04 2.06E−030.3613207 N2 2.21E−07 3.26E−05 3.26E−05 3.26E−05 2.21E−07 2.21E−074.66E−04 6.47E−07 6.18E−07 0.4279003 IC4 3.44E−04 1.23E−03 1.23E−031.23E−03 3.44E−04 3.44E−04 0.0247203 3.33E−03 0.0204513 0.0206331 CUCL0.0894273 0.0885729 0.0885729 0.0885729 0.0894273 0.0894273 2.95E−117.26E−13 0 3.15E−14 ANILINE 0.3715804 0.36803 0.36803 0.36803 0.37158040.3715804 0.4581486 0.4930622 0.6646093 4.91E−04 NMP 0.5380702 0.5329290.532929 0.532929 0.5380702 0.5380702 0.4684502 0.4997972 0.30385615.01E−04 Total Flow 1505.59 1552.86 1552.86 1552.86 1505.59 1505.595.89E−03 0.4095263 0.0336387 16.18674 lbmol/hr Total Flow 1455081.47E+05 1.47E+05 1.47E+05 1.46E+05 1.46E+05 0.5027346 38.89952 3.073815470.5613 lb/hr Total Flow 2000 2063.515 9563.191 13833 2058.304 2058.5218.16E−03 0.6204605 0.04765 825.9148 cuft/hr Temperature F. 90 105.096195.53801 140 158 158.2431 −20 90 −20 96.94405 Pressure psia 117.6959114.6959 25 25 25 118.6959 114.6959 24.9 24.8 114.6959 Vapor Frac 0 00.020591 0.0297334 0 0 0 0 0 1 Liquid Frac 1 1 0.9794089 0.9702665 1 1 11 1 0 Solid Frac 0 0 0 0 0 0 0 0 0 0 Enthalpy −60439.71 −58273.13−58273.13 −56229.58 −57622.43 −57585.8 −49592.05 −47471.61 −28177.63−8659.402 Btu/lbmol Enthalpy −625.377 −615.9475 −615.9475 −594.3472−596.2263 −595.8472 −581.0902 −499.7715 −308.3662 −297.8729 Btu/lbEnthalpy −9.10E+07 −9.05E+07 −9.05E+07 −8.73E+07 −8.68E+07 −8.67E+07−292.1342 −19440.87 −947.8608 −1.40E+05 Btu/hr Entropy −112.3696−109.6524 −109.5691 −106.0242 −107.4881 −107.4788 −111.4813 −112.727−110.4079 −19.64671 Btu/lbmol-R Entropy −1.162701 −1.159027 −1.158146−1.120676 −1.112192 −1.112096 −1.306271 −1.186767 −1.208266 −0.6758228Btu/lb-R Density 0.75276 0.7525312 0.1623788 0.1122576 0.73147130.731394 0.7221323 0.6600361 0.7059546 0.0195985 lbmol/cuft Density72.75067 71.19494 15.36222 10.62039 70.69322 70.68575 61.62902 62.694664.50811 0.5697456 lb/cuft Average MW 96.64524 94.6073 94.6073 94.607396.64524 96.64524 85.34311 94.98663 91.37714 29.0708 Liq Vol 60 F.2474.029 2538.765 2538.765 2538.765 2474.029 2474.029 8.78E−03 0.61656120.0501975 18.42872 cuft/hr Substream: MIXED V1FLARE V2 V3 VAP-RECVAPFEED Mole Flow lbmol/hr C2 = 3.172573 39.91302 39.9096 39.9086143.08116 C2 5.653708 4.940621 4.940017 4.939807 10.5935 N2 7.1877210.1700194 0.1700186 0.1700185 7.357739 IC4 0.1668301 2.253242 2.2520962.251014 2.417848 CUCL 4.78E−22 2.85E−13 2.86E−24 0 0 ANILINE 9.19E−060.20608 0.022065 1.29E−04 0 NMP 3.17E−06 0.1961404 9.44E−03 2.06E−05 0Mole Frac C2 = 0.1960697 0.8371173 0.843697 0.8442764 0.6789755 C20.3494075 0.1036223 0.104433 0.1045028 0.1669576 N2 0.4442117 3.57E−033.59E−03 3.60E−03 0.1159608 IC4 0.0103103 0.0472584 0.0476097 0.04762070.0381062 CUCL 2.95E−23 5.99E−15 6.04E−26 0 0 ANILINE 5.68E−07 4.32E−034.66E−04 2.73E−06 0 NMP 1.96E−07 4.11E−03 2.00E−04 4.36E−07 0 Mass Flowlb/hr C2 = 89.00261 1119.71 1119.614 1119.587 1208.589 C2 170.005148.5627 148.5445 148.5382 318.5427 N2 201.3531 4.762835 4.7628124.76281 206.1159 IC4 9.69673 130.9661 130.8995 130.8366 140.5336 CUCL4.73E−20 2.83E−11 2.83E−22 0 0 ANILINE 8.56E−04 19.19188 2.0548830.0120247 0 NMP 3.14E−04 19.4439 0.9360284 2.04E−03 0 Mass Frac C2 =0.1893437 0.7761549 0.7958521 0.797575 0.645 C2 0.3616676 0.10297990.1055895 0.1058162 0.17 N2 0.4283574 3.30E−03 3.39E−03 3.39E−03 0.11IC4 0.0206287 0.0907823 0.0930468 0.0932058 0.075 CUCL 1.01E−22 1.96E−142.01E−25 0 0 ANILINE 1.82E−06 0.0133033 1.46E−03 8.57E−06 0 NMP 6.69E−070.013478 6.65E−04 1.46E−06 0 Total Flow 16.18085 47.67913 47.3032447.2696 63.45025 lbmol/hr Total Flow 470.0586 1442.638 1406.812 1403.7381873.781 lb/hr Total Flow 634.7071 12547.34 11089.96 8812.544 1155.656cuft/hr Temperature F. −20 158 90 −20 0 Pressure psia 114.6959 25 24.924.8 226.6959 Vapor Frac 1 1 1 1 0.9823996 Liquid Frac 0 0 0 0 0.0176004Solid Frac 0 0 0 0 0 Enthalpy −9795.256 13137.72 12629.88 11470.015793.013 Btu/lbmol Enthalpy −337.1825 434.201 424.6725 386.242 196.1639Btu/lb Enthalpy −1.59E+05 6.26E+05 5.97E+05 5.42E+05 3.68E+05 Btu/hrEntropy −21.92954 −18.274 −19.22263 −21.55552 −25.0739 Btu/lbmol-REntropy −0.7548814 −0.603955 −0.6463497 −0.7258623 −0.8490563 Btu/lb-RDensity 0.0254934 3.80E−03 4.27E−03 5.36E−03 0.0549041 lbmol/cuftDensity 0.7405913 0.1149756 0.1268545 0.1592887 1.6214 lb/cuft AverageMW 29.05031 30.25722 29.74029 29.69643 29.5315 Liq Vol 60 F. 18.4199465.35257 64.78621 64.73601 83.15566 cuft/hr

At least one embodiment is disclosed and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R_(l), and an upperlimit, R_(u), is disclosed, any number falling within the range isspecifically disclosed. In particular, the following numbers within therange are specifically disclosed: R=R_(l)+k*(R_(u)−R_(l)), wherein k isa variable ranging from 1 percent to 100 percent with a 1 percentincrement, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5percent, . . . 50 percent, 51 percent, 52 percent . . . 95 percent, 96percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover,any numerical range defined by two R numbers as defined in the above isalso specifically disclosed. Use of the term “optionally” with respectto any element of a claim means that the element is required, oralternatively, the element is not required, both alternatives beingwithin the scope of the claim. Use of broader terms such as comprises,includes, and having should be understood to provide support fornarrower terms such as consisting of, consisting essentially of, andcomprised substantially of. Accordingly, the scope of protection is notlimited by the description set out above but is defined by the claimsthat follow, that scope including all equivalents of the subject matterof the claims. Each and every claim is incorporated as furtherdisclosure into the specification and the claims are embodiment(s) ofthe disclosed inventive subject matter. The discussion of a reference inthe disclosure is not an admission that it is prior art, especially anyreference that has a publication date after the priority date of thisapplication. The disclosure of all patents, patent applications, andpublications cited in the disclosure are hereby incorporated byreference, to the extent that they provide exemplary, procedural orother details supplementary to the disclosure.

What is claimed is:
 1. A system comprising: a first polymerizationreactor for polymerizing olefin monomers to yield a mid-polymerizationproduct stream; a separator for separating the mid-polymerizationproduct stream into a mid-gas stream and a mid-polymer stream; and asecond polymerization reactor for polymerizing the mid-polymer stream,wherein the mid-gas stream comprises ethane, unreacted ethylene, andhydrogen.
 2. The system of claim 1, wherein the separator comprises aflash tank for reducing a pressure of the mid-polymerization productstream so as to flash ethane, unreacted ethylene; hydrogen, orcombinations thereof.
 3. The system of claim 1, wherein themid-polymerization product stream comprises hydrogen, ethane, unreactedethylene, isobutane, and polyethylene; and wherein the mid-polymerstream comprises polyethylene and isobutane.
 4. The system of claim 1,further comprising: an absorption reactor for contacting the mid-gasstream with an absorption solvent system to absorb at least a portion ofthe unreacted ethylene from the mid-gas stream and to yield ethane in awaste gas stream.
 5. The system of claim 4, further comprising: aprocessing device to receive ethane from the absorption reactor and toconvert ethane to ethylene, wherein the processing device is a cracker,a catalytic cracker, a converter, a dehydrogenator, or combinationsthereof.
 6. The system of claim 5, wherein ethylene is recycled from theprocessing device to one or more of the first polymerization reactor andthe second polymerization reactor.
 7. A system comprising: a firstpolymerization reactor for polymerizing olefin monomers to yield amid-polymerization product stream; a separator for separating themid-polymerization product stream into a mid-gas stream and amid-polymer stream; a second polymerization reactor for polymerizing themid-polymer stream; and a scavenger stream for introducing a scavengerprior to the second polymerization reactor, wherein the mid-gas streamcomprises the unreacted ethylene and the ethane.
 8. The system of claim7, wherein the scavenger stream introduces the scavenger to themid-polymerization product stream.
 9. The system of claim 7, wherein thescavenger stream introduces the scavenger to the separator.
 10. Thesystem of claim 7, wherein the scavenger stream introduces the scavengerto the mid-polymer stream.
 11. The system of claim 7, wherein thescavenger comprises a hydrogenation catalyst.
 12. The system of claim 7;wherein the separator comprises a flash tank for reducing a pressure ofthe mid-polymerization product stream so as to flash unreacted ethyleneand ethane.
 13. The system of claim 7, wherein the mid-polymerizationproduct stream comprises ethane, unreacted ethylene, isobutane, andpolyethylene; and wherein the mid-polymer stream comprises thepolyethylene and the isobutane.
 14. A system comprising: a firstpolymerization reactor for polymerizing olefin ers to yield amid-polymerization product stream comprising hydrogen; a first separatorfor degassing at least a portion the hydrogen from themid-polymerization product stream to yield a hydrogen-reduced productstream; a second separator for separating the hydrogen-reduced productstream into a mid-gas stream and a mid-polymer stream; and a secondpolymerization reactor for polymerizing the mid-polymer stream; whereinthe mid-gas stream comprises unreacted ethylene and ethane.
 15. Thesystem of claim 14, wherein the mid-polymerization product streamfurther comprises ethane, unreacted ethylene, isobutane, andpolyethylene.
 16. The system of claim 14, wherein the mid-polymer streamcomprises polyethylene and isobutane.
 17. The system of claim 14,wherein the second separator comprises a flash tank for reducing apressure of the hydrogen-reduced stream so as to flash unreactedethylene and ethane.
 18. The system of claim 14, wherein an amount ofhydrogen in the mid-gas stream comprises less than about 1 wt %.
 19. Thesystem of claim 14, further comprising: an absorption reactor forcontacting the mid-gas stream with an absorption solvent system toabsorb at least a portion of the unreacted ethylene from the mid-gasstream and to yield ethane in a waste gas stream.
 20. The system ofclaim 19, further comprising: a processing device to receive ethane fromthe absorption reactor and to convert the ethane to ethylene, whereinthe processing device is a cracker, a catalytic cracker, a converter, adehydrogenator, or combinations thereof.